Spooncraft

Neth discussed the planned changes and went a little bit deeper in detail than previously mentioned…

With haste gear you can work toward lowering the GCD down to 1 second, but it will take more than just gear to max it.
You can max it with the use of both haste on gear and abilities/talents. (src)

Essentially what this breaks down to is the spell haste stat budgeted on items can only do so much, but when coupled with talents that improve casting speed, abilities like the troll racial or a shaman’s heroism/bloodlust, and other haste items like trinkets or the leatherworking made drums can bring the GCD to a point where a caster can be firing off spells like a chain gun.