So how is haste good for casters?

higher throughput = higher damage per second

>Lock
>Life Tap
>trolololol

But yeah, mostly what others have said. More haste means more ticks for hots/dots, faster casting in general, and while I haven't play all caster classes, I assume most of them have at least one means of mana regen.

Contrary to belief, haste isn't primarily used to reduce the cast time on your spells.

Haste is actually used to give your Over Time spells more ticks, thus making it the best stat for classes such as Warlocks, Fire Mages, Restoration Druids and other classes that heavily rely on ticking damaging/healing for maximum throughput.

quote Etherlight

The only class I can recall that has any kind of mana issue would be arcane mages, but even then they have Evocation to somewhat alleviate their issue. The rest of the casters, however, doesn't have mana issues a all.

Actually, Arcane Mages have all the tools they need to keep their mana up the whole duration of a fight. Arcane Mages have Evocation, Mana Gems and Mage Armor.

Arcane Mages have two damage phases, Burn and Conservation. Basically the Burn phase is pop all your cooldowns, mash Arcane Blast till 70% mana, pop your mana gem, continue mashing Arcane Blast till 30% - Evocate then build your Arcane Blast stacks to 4 and use your Arcane Missiles to reset your Arcane Blast's stacks (Conservation Phase). Rinse and Repeat when your cooldowns are back.

So how does Haste come in to play for Balance Druids?