Soloing classic content

Because stats grow exponentially every expansion, most end-game raid content from previous expansions becomes soloable by players at max level of the current expansion. There are many incentives to solo old content, like obtaining old legendary items or mounts, and completing old achievements.

Cataclysm, in particular, was notable in the extreme stat scaling compared to previous expansions. In particular, Razorgore the Untamed, Lady Vashj, and the Lich King have been soloed although such a feat was previously thought to be impossible. In addition, encounters such as Gehennas and Vaelastrasz the Corrupt that have been difficult in the past have become almost trivial.

Blood Death Knights are by far and away currently the best, and simplest class to solo large amounts of content with for the most part; as tanks, they have the ability to mitigate large amounts of damage, and their self-healing design allows them to sustain incoming damage without a healer. Other classes that are able to solo, albeit with more limitations and difficulty, include Hunters, feral and balance Druids, and Warlocks.

Molten Core
With the advent of Cataclysm, Molten Core has become almost trivial to solo for most level 85 classes.

Temple of Ahn'Qiraj
Most of AQ40 is relatively easy to solo. Viscidus will prove impossible for many classes to solo due to reliance on heavy frost damage. The Twin Emps requires heavy DPS, as only with the advent of Cataclysm have players been able to single-handedly burn through 30,000 HPS done by the brothers. Lastly, C'Thun, previously thought unsoloable, is soloable only by kiting Ouro into the boss' room; this will allow him to pull the player out of C'Thun's stomach before he is instantly killed and the encounter reset.

General tips

 * Regardless of which expansion they were introduced, Level ?? Raid bosses are always considered three levels higher than the highest level character in the instance when determining base chance to be hit, chance to hit, chance to dodge or parry or be dodged or parried, weapon skill, and defense. All other level-dependent stats are the same for Hakkar as they are for The Lich King. This means that your defense, hit rating, and expertise should be the same as they would be for any current raid.

Death Knight
With the 4-piece T10 tank set bonus, 3/3 Improved Rune Tap, Vampiric Blood, Anti-Magic Shell, Icebound Fortitude and, you will have a long string of defensive cooldowns. Raise Dead followed by Death Pact should only be used as a last resort; it's too good to waste before you really need it. Empower Rune Weapon is also a defensive cooldown for emergency situations; immediately allowing use of at least two Death Strikes at once.

Don't forget that you can also spec into situational talents like Lichborne, which will allow you to heal yourself with Death Coil, or Bloodworms for a minor HPS gain, but these talents are not normally part of current raid tanking specs; you would only use them for PvP, DPS, or "solo old content" specs.

As of Patch 4.0.1, Death Strike no longer requires diseases on its target to heal. You don't need to keep diseases up to solo old fights anymore.

Hunter
Because the majority of damage intake will be to your pet, a Tenacity pet is preferred. Give it a defensive spec, like this one (note that a Exotic Beasts spec is required), and use Aspect of the Viper and cast Mend Pet as necessary (spec into Improved Mend Pet; especially important for bosses that apply debuffs, like most in Molten Core), and.

On bosses with enrage timers, this tactic may not work so well; help DPS if you must, Roar of Sacrifice will help if you do pull aggro, and be sure to carry an so that you don't run out of mana for Mend Pet.

Paladin
You're in luck - if you're the only person in an encounter, you can use Divine Shield as much as you like without worrying about mobs ignoring you. Make sure to take necessary Protection talents to reduce the cooldown of Divine Shield and Hammer of Justice - the latter is extremely useful in some fights. Use Seal of Light or Seal of Wisdom depending on the encounter - but usually, SoW will suffice.

Warlock
Metamorphosis (warlock ability) will make you immune to critical hits from level ?? raid bosses and make your armor and stamina as high as a moderately geared tank for 30 seconds. In addition, you retain all your DPS abilities, allowing you to effectively tank the boss as well as deal massive amounts of damage. You may defeat the boss before Metamorphosis lifts, but if not, rely on your Voidwalker to resume tanking. For longer boss fights, careful threat management with Suffering (Voidwalker pet taunt) and Soulshatter (warlock ability) (Warlock aggro drop) may be required. There may be times when, a la Classic, you may be required to slow down or even hold back your fire to allow your pet to build the required amount of threat.

Classic fights that cannot be soloed
The following Classic fights have mechanics which specifically require more than one person to overcome:
 * in Blackwing Lair: if he is killed before all the eggs in the room are destroyed, he will explode, causing AoE damage that will one shot the entire raid, goes through Divine Shield and Ice Block, and death from this ability is not prevented by Ardent Defender.
 * in the Temple of Ahn'Qiraj: if there is no one outside his stomach when one player is teleported in, that player dies.