Dual wield

Dual wield allows the character to hold a weapon in each hand (main hand and off hand). The character can deal some damage with the weapon in the off-hand between strikes with the strong hand. This is a very important passive ability as it allows a character to deal significantly more damage as compared to a single one-handed weapon. Once it is acquired, the character will immediately begin to strike with each hand (if there is a weapon in each) while in battle.

Warriors, monks, rogues, death knights and shamans are all able to dual wield weapons, however there are some limitations:
 * Demon hunters and rogues of any specialization are able to dual wield weapons at creation.
 * Frost death knights, Fury warriors, Enhancement shamans and Brewmaster and Windwalker monks are able to dual wield from level 10 (when specialization become available to the player).
 * Hunters of any specialization are able to dual wield weapons at creation. However most of their ability require either a ranged or a two-handed weapon, meaning it is not useful for gameplay purposes.
 * Feral and Guardian druids are able to dual wield Fangs of Ashamane and Claws of Ursoc.

A weapon equipped in the main hand will deal full damage, while an off-hand weapon will deal 50% of its damage.

Most disarm effects do NOT affect off-hand weapons. While abilities that require a weapon in the main hand can't be used, the off-hand weapon will still deal its regular damage. The rogue disarm Dismantle removes both main-hand and off-hand equipment.

Miss chance
Dual wielding adds a 19% miss penalty to both main and offhand weapons. The base miss rate for all characters is 5%, so each weapon by itself has a 24% chance to miss (19% + 5%). Important note: Prior to version 1.8, dual wield's miss chance had a hard cap of 19%, meaning that all dual-wield auto-attacks had a minimum 19% miss chance regardless of how much +hit% gear was equipped. In version 1.8, this hard cap was removed. The exact wording of the 1.8 patch note was:


 * "Items which provide +hit chance will now be allowed to counteract the increased miss chance penalty of dual-wielding."

Take a level 80 rogue for example vs. a level 83 raid boss: the rogue has 5% + (0.04% * 15) = 5.6% base miss chance, plus 19% dual wield miss chance, leaving us with a total miss chance of 24.6%.

Note that the +19% miss chance for dual-wielding only applies to ordinary auto-attack melee attacks. It does not apply to any special attack powers that cost rage, energy, or mana -- instant attacks such as Sinister Strike, Stormstrike or Heroic Strike do not incur the dual wield miss penalty. So, with 9% +hit from gear/talents a dual-wielder will never miss with an instant attack (although the attack can still be dodged, parried, or blocked -- see the Attack table article). However, a dual-wielder would need 25% +hit if he wants to remove the miss chance for auto-attack/white damage totally.

Chance on hit proc rate
Some weapons have special abilities that will occur (or "proc") on some hits. These abilities are preceded in the weapon's description by the words "Chance on hit:".

The chance for one of these abilities to proc on a successful auto-attack strike is independent of whether the weapon is being wielded in the main hand or wielded in the off hand. However, these abilities also have the same per-strike chance to go off when making an instant attack (such as Sinister Strike, Mongoose Bite, Overpower, etc.). Instant attacks are always assumed to be made with the weapon in the main hand only. This means that over the course of a normal fight in which several instant attacks are used, a given weapon's chance-on-hit ability will go off more often if the weapon is wielded in the main hand than if it is being wielded in the off hand. The exceptions to this are the shaman Stormstrike ability, the rogue Mutilate ability and the warrior Whirlwind ability, in which all three abilities give an extra instant attack with both wielded weapons.

Proc rate for other weapon abilities
Some weapons have abilities that go off some of the time, but are not listed as "Chance on hit:". For example, the Crusader enchant reads "... often when attacking in melee ...", and the Misplaced Servo Arm's ability reads "Equip: Chance to ...". The proc chances for these kinds of abilities are separate and distinct from the "Chance on hit:" abilities discussed above.

The proc rate for these abilities is generally based on an average rate per minute, not a chance per strike. Whether the proc rate for such an ability on a one-hand weapon is affected by which hand the weapon is wielded in is something that needs to be experimentally verified.

Mists of Pandaria
Before Mists of Pandaria, hunters were able to dual-wield melee weapons, but with the removal of a special ranged weapon slot and the ability for hunters to efectively use melee weapons, they have no need to do so. However, it still is useful for roleplay purposes.

Legion
With the introduction of artifacts, Feral and Guardian druids received Fangs of Ashamane and Claws of Ursoc respectively, allowing them to dual wield. This fact as well as the druid exclusive Dreamgrove Blade might suggest druids were planned to have dual wielding added to them permanently.

However, excluding these two artifacts, druids have not been able to dual wield any other weapons since.