Haste increases attack speed.
Haste stacks in a multiplicative manner. This means that it is beneficial to stack multiple haste effects. For instance, stacking Slice and Dice with Blade Flurry(Rogue abilities) gives a total of 68% haste (140% * 120% = 168% of the base attack speed). Haste rating stacks additively with itself (two sources of 100 haste rating give 200 haste rating stacked together) and then is converted into a percentage that stacks in a multiplicative manner with other sources of haste. For every 32.79 points of haste rating you will have 1% faster attack speed at level 80.
The formula for determining weapon haste speed at level 80 is:
Example: Beast Master Hunter
|Haste Rating Required Per 1%|
|Level 60||Level 70||Level 80|
In World of Warcraft: Cataclysm, haste will also increase the rate at which you gain energy, runes, and focus. Retribution paladins and Enhancement shaman will have a talent that allows them to take advantage of this benefit.
Early numbers are showing a 32.79 rating required at level 80 to achieve a 1% gain in speed.
Quivers and ammo bags no longer grant haste. Instead, the haste from quivers and ammo bags has been built into Auto-Shot. Some classes' haste got buffed and now 25.21 Haste Rating provide 1% melee haste for Death Knights, Druids, Shamans, and Paladins.
As of patch 3.0, Haste Rating also increases your Spell haste.
Haste has been rebalanced. It has returned to the ratios from the launch of Burning Crusade. Melee attacks and spell casts will now benefit at identical rates from haste. This change results in a reduction in the benefit of haste for melee attacks and an increase in the benefit for spellcasters.
- See also: Patch 2.2.0 (Release Notes)
The amount of haste granted by a point of haste rating is being reduced again. See combat rating system for current rating effects.
10 haste rating gives 1% haste at level 60.
Previously, haste and slow effects worked inconsistently, with spells working differently from weapons, and hastes and slows not acting as inverses of each other. We have revised the system so that all haste and slow effects work the same way, and haste and slow percentages of the same magnitude perfectly cancel each other out (30% haste and 30% slow combine to no change). As a result, we had to change the tooltip numbers on all spell haste effects, and on all melee and range slow effects. The numbers in the tooltips are different, but the game functionality is unchanged (other than slight rounding errors). Those tooltips that changed will now display larger numbers than they used to display. Conceptually, haste values indicate how much more of that activity you can perform in a given time. 30% melee haste means 30% more swings in a given time. Slow values indicate how much longer an activity takes to complete. 30% slow means an action takes 30% longer to finish.
Haste now stacks in a multiplicative manner.
Changes are likely coming for haste in Patch 3.3.0. Here's a post from the lead developer describing some changes that might be seen:
More detailed comment regarding all stats for Patch 4.0.1 and eventually World of Warcraft: Cataclysm, but here referencing only haste.