Spell haste and you

I promised to write about spell haste, didn't I? I will be more careful what I promise in future. Some of the discussions of haste are mind-numbingly obtuse. They make my eyes bleed. I don't have much direct experience of haste either, so can't claim to be an expert. I'm going to give you the idiot's guide instead. By that, I mean it's written by an idiot, not for them, so please take everything I say with a pinch of salt...

Know haste, love haste
Spell haste is a stat you find on some badge and raiding gear. It reduces the casting time of direct and channelled spells, and reduces the global cooldown (to a minimum of one second). It works in exactly the same way as other hasty effects you may know, such as bloodlust, berserking and icy veins. Effectively, it speeds up your spell rotation enabling you to do more damage in the same space of time.

It takes 15.7 haste rating to get 1% spell haste, and 1% spell haste will reduce the associated time by 1%. So with 1% spell haste, my 1.5-second mind blast is reduced to 1.485 seconds, and a 3-second mind flay will take 2.97 seconds. If I plucked from thin air the random figure of 30 and ascribed that as the average number of spells cast in one minute, I would be able to cast one additional spell in the space of 3 minutes, 20 seconds.

So you can see at small numbers it provides a very modest benefit that probably only kicks in on boss fights. But as your haste rating increases, the time at which the benefit kicks in gets shorter and you can squeeze more and more spells in.

Sort of.

Haste shmaste
What haste does not do is reduce your spell cooldowns. So even with haste, the time between your shadow word: deaths and mind blasts will never shrink. The best you can hope for is that haste presents you with more opportunities to use them.

Neither does it affect the duration of your dots. That's annoying, because it means that while you may be saving time on each spell cast, your spell rotation is still essentially anchored to the fifteen-second cycle of vampiric touch.

If my maths is correct, it will take somewhere between 11-12% haste to save enough time for an extra cast between vampiric touches. Before that point — and indeed, after it — you must either cast an extra spell and live with the lost up-time, or recast straight away and overlap.

Overlapping dots is clearly the lesser of two evils. It probably isn't going to hurt your dps, but it is going to eat into your mana. This on top of the fact that you are casting quicker anyway. So haste is a double-edged sword — you will do more damage faster, but you will run out of mana quicker.

The misery verdict
If I were one of those single spell-spamming classes, like a mage or a destro lock, I would eat haste up with a spoon. It's a no-brainer — cast more often, crit more, do more damage. But I'm not. I'm essentially a dot class, whose damage and utility is dependent upon maintaining maximum uptime of spells that remain infuriatingly intractable to haste. Is that right? Is that fair? I don't know. But it's not something that's going to change any time soon.

Spell haste can and will enable me to set up those dots faster, and cast faster in-between applications. So there is a dps boost. But I am deeply suspicious of any claim that haste is of more than marginal interest to shadow priests in its current form. I've seen one claim that says 1 spell haste equals 1 spell damage at 1400 spell damage. That was for locks, so I'm not sure if the claim is made across the board. Either way, that's a figure I can only aspire too, but I promise I will keep my mind open as I pick up more haste.