Patch 4.0.1 (undocumented changes)

Stat changes

 * Stamina &mdash; Due to the assigning of Strength, Agility, and Intellect, non-plate wearers have more Stamina than before. Health pools are now much closer between plate-wearers and other classes. Health per point of stamina has been increased from 10 to 14.
 * Spirit &mdash; This stat should only be found on healing gear. Non-healing casters have other systems in place to regenerate mana.
 * Intellect &mdash; Intellect now grants Spell Power in addition to increasing your maximum mana and increasing your Critical Strike chance with spells.
 * Haste &mdash; Haste should now be more attractive for melee classes by allowing them to recover resources such as rage, energy, and runes more quickly. Our intention is for Haste to let you "do stuff" more often.
 * Parry &mdash; Parry provides the same avoidance as Dodge, and you'll receive a percentage of your strength as Parry Rating.
 * Mastery &mdash; This is a new stat that will allow players to become better at whatever makes their chosen talent tree cool or unique. It's directly tied to talents, so what you gain from improving this stat is entirely dependent upon your class and the talent specialization you choose.  We’ll talk more about specific Mastery benefits in the future.
 * Armor &mdash; The amount of bonus Armor received per stat point on items has been drastically reduced, and Armor is no longer given by Agility. In addition, Armor now better mitigates differences among Armor types so that protection from mail, leather, and cloth is much closer to that of plate.
 * Resilience &mdash; This now only affects damage done by players and their pets. It will not impact crit chance, crit damage, mana drains, or other such effects.

Removed from items

 * Attack Power &mdash; This stat is rarely present on items, although it is derived from other stats. Strength and Agility, which are present on items, grant the appropriate amount of Attack Power (generally 2 Attack Power per point of Strength or Agility) depending upon which stat a particular class favors.
 * Block Rating &mdash; Block has been redesigned to scale better. Blocked attacks will simply hit for 30% less damage.  Block Rating is no longer given out directly as a stat.  Instead, Mastery for Protection paladins and Protection warriors increases the chance to block.
 * Spell Power &mdash; Spell Power is no longer present on most items. Instead, as mentioned above, Intellect now grants Spell Power.  One exception is that caster weapons still have Spell Power.  This allows us to make weapons proportionately more powerful for casters in the same way they are for melee classes.
 * Armor Penetration &mdash; This stat is no longer present on items. Armor Penetration still exists in talents and abilities.
 * Shield Block Value &mdash; There are some effects that increase the Block value by a percentage, but this does not exist as a stat.

Removed from the game

 * MP5 &mdash; This stat no longer exists in the game. Holy paladins and Restoration shaman have been redesigned to benefit from Spirit.
 * Defense &mdash; Defense is now removed from the game. Tanking classes will become uncrittable versus creatures by shifting into Defensive Stance, Blood Presence, or Bear Form, or by using Righteous Fury.
 * Spell Ranks &mdash; Spell ranks now cease to exist. All spells have one rank and will scale appropriately by caster level.  The levels at which you can learn certain spells have been changed in order to fill in some of the gaps, and there are many new spells to learn along the way as well.
 * Weapon Skill &mdash; This stat will be removed from the game completely. Classes will start with all the weapon skills they need to know and will not need to improve them.

What else you should know

 * Combat ratings &mdash; Ratings are much harder to "cap out" at maximum gear levels. Ratings are steeper in Cataclysm, and creatures in later tiers of content will be harder to hit or crit, similar to how level-83 mobs are harder to hit or crit than level-80 mobs.
 * Reforging &mdash; This new itemization customization feature allows you to partially change the stats on an item. You can reduce the value of an existing stat on an item, and add an equivalent amount of another stat that was not already present on the item.  This makes it far easier to reach important thresholds like the Hit Rating and Expertise Rating caps.

Player versus Player

 * Battlegrounds will no longer close when both sides are below the minimum player requirement.
 * There is a soft cap of 4000 honor points. Once over the cap you will not earn any more honor, nor be able to refund items to the quartermasters until you are under the cap.
 * Players level-capped due to not having the next expansion are now placed in the same battleground brackets as those who have experience turned off.
 * Arena skirmishes have been removed.
 * War Games have been added.

Achievements

 * New Feat of Strength added:.
 * and converted to Feat of Strength.
 * In Dungeons & Raids section of achievements all Lich King Heroics have been put to Lich King Dungeon tab.

Talents

 * A total of 36 points at level 80 (down from 71).
 * Each tree only requires 31 points to reach the last tier (down from 41).
 * You must now select only one tree. Once you do, you are given a primary ability for that spec, and two or three attributes specific for that spec. At level 80, you are given a Mastery trait also specific for the spec you chose, learned at your trainer.
 * You cannot put points into any other tree until you have put 31 into your first tree.

Experience
The maximum experience needed to level from 1-40 has been reduced by a significant amount.

Classes

 * The price of dual specialization is reduced from 1000 gold to 100 gold.
 * Health regeneration uses a new formula. Outside of combat, all classes seem to regenerate 0.75% of their maximum health per second before the effects of abilities.
 * Mana regeneration uses a new formula.
 * Class buffs can no longer be applied to player-controlled pets.
 * Class buffs and their raid-wide counterparts have been consolidated into a single spell. When the target of the buff is within your party or raid (including yourself), the buff applies to the entire raid.  Reagents are no longer required for these abilities.
 * Dispell abilities will no longer be prevented from casting when the target does not have a valid debuff to dispell. It will consume the mana cost of the ability and global cooldown despite doing nothing.

Mage

 * Frost mages can rename their summoned Water Elemental using /run PetRename("name").

Mounts

 * All mounts now scale with riding skill - level 20 60% mounts will now move at 100% speed with journeyman riding.
 * The X-53 Touring Rocket can now also be used as a ground mount.
 * Players can now instantly transition in Dalaran with mounts that have both a ground and flying speed without remounting.
 * If a player upgrades the riding skill while riding a mount that can scale to the new skill, it is applied instantly. For example, learning Expert Riding in Outland while riding a Celestial Steed immediately enables flying without remounting.
 * Players will no longer get a letter in the mail from their riding trainer upon reaching the appropriate level to learn the next riding skill. The riding skill now displays in the "General" tab in the spell book and players are alerted to train riding just like other new abilities.

Dungeons

 * Though not displayed in the Dungeon Finder Interface Screen, completing a Random Lich King Heroic Dungeon using the Dungeon Finder will award 23 Justice Points, in addition to the 16 Justice Points earned for each boss killed.
 * Completing a weekly raid quest will be rewarded with 137 Justice Points.
 * After a hotfix, The Essence-Infused Moonstone is no longer needed to summon Anzu; he will now always be present in Heroic Sethekk Halls.

Professions

 * Herbalism and Mining give XP. The higher level the char is, the lower the received XP will be.  This uses rest XP so you will get double XP while you have sufficient rest stored up.
 * Tiffany Cartier no longer exchanges Titanium Powder for Dalaran Jewelcrafter's Tokens; you now turn them in at Timothy Jones via a repeatable quest.
 * Master Riding is available from Northrend Riding trainers at a cost of, allowing all flying mounts to scale to 310% speed. Characters that already had a 310% speed flying mount pre-4.0.1 are given this skill automatically and free of charge.  Note that reputation discounts apply to the trainers in the Northrend starting areas!
 * The exception is the the Reins of the Violet Proto-Drake from the meta world events achievement . While still technically a 280% mount due to Patch 4.0.1, this mount will award 310% speed to characters who do not have it for free, due to a hotfix.
 * The speed of nearly all mounts scales with riding skill. Exceptions include the Sea Turtle mount.
 * Cold Weather Flying is now available to all characters at level 68 for.
 * Engineers can no longer build ammo (it is no longer used for ranged weapons).
 * Flexweave Underlay, Springy Arachnoweave, and Nitro Boosts no longer increase spell power, agility, and crit rating respectively, but can now be used alongside other enchants.
 * Leatherworking Specializations have been removed
 * Tailoring Specializations have been removed; specialty cloth is now always made in single units.
 * There is now just one kind and tier of Vellum. Old Weapon and Armor Vellums are converted to a Ruined Vellum, which can be used to create the new all-purpose Enchanting Vellum.
 * Alchemy Transmute cooldowns have been redesigned. Completing the transmute will now cause a cooldown that is fixed to reset at 00:00 server time, limiting you to one cooldown per day.
 * Many profession trainers in capitals now train professions up to Grand Master. Accounts without expansions will still be unable to access the professions associated with those expansions.
 * Enchant Shield - Lesser Block now grants 10 parry rating rather than 10 block rating due to the removal of block as a stat.
 * Enchant Bracer - Minor Dodge, Enchant Bracer - Lesser Dodge, Enchant Bracer - Dodge, and Enchant Bracer - Greater Dodge now grant dodge rating equal to the defense rating they previously gave due to the removal of defense as a stat (2, 3, 5, and 12 respectively).
 * Archaeology has been added to the UI, however there are no Archaeology trainers to teach it.
 * Quests involving obsolete profession specializations have been removed.

Items

 * Some former Guardian Elixirs are now Battle Elixirs.
 * The effect of most scrolls are now considered Battle Elixirs, and will overwrite existing Battle Elixirs. The effect of scrolls of stamina and protection are considered Guardian Elixirs.
 * Most books that formerly taught class spells are now poor-quality items with no function. Exceptions include Tome of Dalaran Brilliance and Tome of Polymorph: Black Cat.
 * has been removed.
 * Conjured Muffin and Conjured Water has been removed.
 * Some glyph items have been replaced with Charred Glyphs, non-functional, poor-quality items.
 * Some glyphs have been replaced or renamed.
 * All old Ammo is now poor quality and is useless. It can still be vendored.
 * Quivers, Ammo Pouches have been converted into regular bags. Most of them have fewer slots than they originally did. The bags can no longer be purchased from vendors or found as drops, but crafted quivers and ammo pouches can still be made as regular bags.
 * Soul Bags have been converted into regular bags. Most of them have fewer slots than they originally did.
 * Numerous item stat changes:
 * Armor Penetration Rating, Block Rating and Defense Rating have been replaced with other stats.
 * MP5 has been replaced with spirit.
 * Spell power on most non-weapon equipment has been replaced with intellect.
 * Wrathful Gladiator gear, with the exception of shoulders and T2 weapons and the tabard, can be purchased for honour, with no Battleground or Arena rating required (although the tooltip says that it is requires)
 * Pristine Black Diamond now has a sell price of 50s
 * Drums of the Wild have changed from a Gift of the Wild buff to a health and mana regeneration buff.
 * Cache of the Ley-Guardian now contains 32 Justice Points instead of 2 Emblems of Triumph.
 * Relics now have stats rather than modifying certain class abilities.
 * Some relics now have sockets. (This includes old-world relics that predated the Jewelcrafting profession.)
 * Several changes were made to gems, mainly hit rating, intellect, and dodge rating moved to blue, red, and yellow (previously yellow, yellow, and red) respectively.
 * The gold cap has been increased to 1,000,000 gold.
 * The original has been renamed to Elementium Ingot, to make way for the new ore that will be added in 4.0.3.
 * The original has been renamed to, to make way for the new bar that will be added in 4.0.3.
 * MOLL-E now binds when used.

Quests

 * The Horde and Alliance versions of the pre-Cataclysm event quest chain was added. Though initially disabled, it was made available November 1, 2010, starting with Earthen Ring emissaries in faction capitals.
 * If you must kill a mob or talk to an NPC, the name of the mob will be visible over their head regardless of user settings. User setting will return once quest is completed.
 * Spirits of Auchindoun (quest) no longer grants any bonus honor.
 * The Morthis Whisperwing (quest) quest chain for druid Swift Flight Form completely removed.
 * Cleanup on Isle E. has replaced Zalazane (quest).
 * Some quests previously offered by Thrall are now offered by Garrosh Hellscream.
 * The Brokering of Peace (Horde) is now tuned in to Shok Narnes rather than Thrall.
 * Messenger to Thrall and Envoy to the Mag'har have been removed.
 * Several quests in Nagrand have been reduced in order to complete, such as the Beast killing quests; and of course the poop quest too.
 * Quests directing newly-leveled characters to their riding trainer have been removed.
 * Arrows Are For Sissies and A Fair Trade (Orgrimmar) have been removed.

Reputation

 * The Gnomeregan Exiles faction has been renamed to Gnomeregan.
 * The most current factions are now listed at the top of the Reputation window. For example, a level 80 character in Northrend will have WotLK rep first, then BC, then Classic factions.

User interface

 * The World Map button has moved to the upper-right corner of the minimap rather than around the edge of it.
 * The Social button has been moved to the upper-left of the chat window.
 * On the Character Select Screen, characters now perform an attack animation appropriate to their class (spell casting or melee) every 30 seconds.
 * Character stats are on a separate display that must be revealed on the right of the character screen.
 * Buttons for popup windows (talents, PvP, dungeon finder, etc.) now display the level at which they become available.
 * The graphics settings window has been revamped.
 * Zone names displayed when moving between zones are now closer to the top of the screen.
 * On the border of the Minimap a yellow arrow points to the closest quest area. In the Objectives frame the number of that quest has a yellow (instead brown) background.
 * While dead a red arrow points in the direction of your corpse on the border of the Minimap.
 * While dead there is a return to Graveyard button at the top of user screen.
 * If quest items can be looted, they will be displayed with a yellow border in the loot window.
 * You can now activate multiple tracking abilities including NPC and profession tracking (Class Trainer, Find Treasure, Track Humanoids, Find Minerals, etc.) simultaneously. The minimap uses appropriate icons to distinguish generic tracking (Class Trainer, Auctioneer, Mailbox, etc.). Dots displayed for other forms of tracking tracking are unchanged.
 * Mounts and companion pets have been moved to the spellbook.
 * Tooltips of mobs and objects displays quest progression of partymembers when in a party and the quest has been shared.
 * The character screen now displays the character's talent specialization if one exists.
 * The background behind the character on the character screen is now greyed.
 * New Guild UI and cap of 1000 members have been implemented.
 * If you unsheathe your weapons while dancing, they no longer get re-sheathed.
 * If you have FPS enabled, it is now displayed on the world map (in a different position than on the main interface)
 * AddOns can no longer get access to Real Names as the UI merely provides a UI Escape Sequence which is rendered as the correct name when displayed.
 * The Kalu'ak boat crew now have their voices follow them around when they speak.
 * Gryphons (the Alliance flight path type) now have their voice remain stationary.
 * All guards and NPC participants at the Tourney now frequently beat their mounts resulting in much noise.
 * Consolidate Buffs is now the default setting and has been turned on for you in your preferences. You can turn it back off of course.
 * A throttle has been added to all public chat channels, limiting players to two messages every few seconds. Players will receive an error message instructing them to wait before spamming sending additional chat in that channel.  Other forms of chat (such as Say, Party, Yell, and Guild) remain unchanged.
 * Links can now be used in all chat channels.
 * Updated generic portraits are used for Night Elf, Gnome, and Troll party/raid members who are out of visual range.
 * The new raid frame interface allows players to select their role within the raid (the leader/assistants can also set it for them). An option Interface allows players to be grouped together by roles.
 * The new raid frame interface allows colored markers to be placed on the ground.
 * When placing a raid target icon on a target, a line will now be displayed in raid chat indicating who placed which icon on what target.
 * The "report problem" button is gone from the Help Request window. In its place is an informational page on Account Security.  You can no longer report issues to the Game Masters without speaking with one unless you are offline when your ticket reaches the top of the queue.
 * GM responses now appear in the corner of the screen (replacing your open GM ticket), rather than in your mailbox. Game Masters may choose to leave a written response even when you are still online rather than open a conversation.
 * New loading screen tips have been added.
 * Having Beginner Tooltips turned on now modifies the description of low level spells to help new players learn when to use them, but replaces the number data with a generalized description (high, low, etc).
 * New loading screen tips have been added.
 * Selection circles for flying units now appear at their flying height rather than on the ground below them (which would disappear above a certain distance).
 * Talents which grant spells have a yellow border in the Talent frame.
 * Instant Quest Text has been removed from the interface menu. It is now turned on permanently.
 * The flight path map window is now larger.

Game engine

 * PowerPC is no longer supported
 * It is now impossible for Windows 98 & Windows 2000 users to install World of Warcraft (unsupported since 3.0.2, however could still play on them)
 * It is officially "impossible" to install on Windows 2000, however there is a way to do it unofficially. (This has not been tested on Windows 98!) The game itself isn't incompatible with Windows 2000, just the Launcher requires a small piece of code that Windows 2000 lacks, so loading the game isn't a problem once you get past installation. http://www.techspot.com/vb/topic155005.html has walkthroughs on a few different ways to make it work with Windows 2000. The Wrapper DLL fix is the only one I have tested and succeeded in installing with.
 * The Launcher will now prevent you from accessing the login screen without an active Internet connection. It can still be accessed by bypassing the Launcher.
 * Cinematics are no longer included in the digital download. They can still be installed from the CDs/DVDs.

Graphics

 * There is no way to disable Full Screen Glow via the Video Options menu. This is a permanent change. You can disable this feature using an in-game console command and restarting the game /console ffxGlow 0

General

 * The Elemental Unrest world event is in the game files. The invasion did not start concurrent with the patch download, but was activated November 1, 2010.
 * Earthquakes have increased in frequency as well as intensity, sometimes causing dust to fall from buildings. Horde and Alliance leaders are meeting to discuss the matter.

NPCs

 * Magni Bronzebeard has new armor and weapons.
 * Garrosh Hellscream has a new, unique model.
 * Alliance Brigadier Generals and Horde Warbringers no longer give the quests Concerted Efforts (quest) and For Great Honor (quest) respectively. They also no longer exchange marks of honor for honor points, although they will still purchase items as vendors.
 * Weapon Masters no longer have gossip text. They cannot be interacted with except through combat. City Guards will no longer offer directions to Weapon Masters.
 * Fei Fei model changed to a pug, from a wolf.

Dun Morogh

 * Operation: Gnomeregan has been removed. The outside of Gnomeregan is now being prepared for the gnomes' relocation.

Durotar

 * Zalazane's Fall has been removed. Zalazane and his minions have been removed, and the Echo Isles are now being prepared for the trolls' relocation.

Nagrand

 * Elemental Unrest phase 3 (November 12, 2010): Thrall, Aggra and Gavan Grayfeather have gathered at the Throne of the Elements.

Orgrimmar

 * Vol'jin, Garrosh Hellscream, and Eitrigg meet with Thrall in Grommash Hold to discuss about recent problems and new leadership.
 * Elemental Unrest phase 3 (November 12, 2010): Thrall has been moved to the Throne of the Elements in Nagrand and will no longer appear in the Hold for the rest of Cataclysm.
 * Shok Narnes, a level 20 orc (possibly a shaman) has been added to Grommash Hold.

Stormwind City

 * Archbishop Benedictus has a new wardrobe, and is now level 80 elite (up from level 60 elite).
 * The Alliance leaders have gathered in the Stormwind Keep's throne room, discussing the recent earthquakes.
 * Gavan Grayfeather, a Wildhammer shaman has been added to the throne room. He stands behind the Alliance leaders, listening.
 * Elemental Unrest phase 3 (November 12, 2010): Alliance leaders have moved back to their respective cities. Gavan Grayfeather now resides in Nagrand.

Thunder Bluff

 * Cairne Bloodhoof now wears two large totems on his back.
 * Aponi Brightmane is now level 80 (up from level 55) and has Paladin abilities.
 * Tahu Sagewind is now level 80 (up from level 55) and has a new outfit.

Flight paths

 * Most flight paths no longer go through as many locations.

Water

 * Flying mounts can land on water, and the character can dismount and re-mount again as long as they do not move. This may be a bug.