Spell Haste

In patch 2.2 Blizzard introduced spell haste as a new attribute to gear. Spell haste like expertise is an attribute on many of the newer items introduced to the game since patch 2.2. Not fully understanding what it does many players tend to overlook it in favor of other stats.

However spell haste is a very powerful attribute that can give you a constant increase in DPS. Spell haste does three things:

• Reduces the time it takes to cast a spell
• Reduces the duration of a channeled spell or damage over time spell without reducing it's damage
  
• Reduces the Global Cool Down

A spell haste rating of 15.7 converts to a 1% haste bonus. That means that an item such as the Drums of Battle will give you a haste bonus of 5%. Another way to think of this is that with a haste bonus of 1% you could cast 101 spells in the time it takes to cast 100. In addition to all this spell haste is applied after any talents that reduce the cast time of a spell! When considering this Spell Haste becomes a lot more relevant as a method of increasing your DPS.

But don't just take my word for it Wow Insider recently reported that almost every member top raiding guild Nihilnum had taken up leather working exclusively to take advantage of the haste rating buff from the Drums of Battle.

(Statistical data sourced from Wowwiki Casting Speed picture from Wowhead)