Schnell!!!11shift

Today we're going to talk about spell haste, and interject every now and then with a random phrase in German.

Like so!

Ich möchte essen kinder kuh.

So.

Spell Haste then.

It is a mechanic that effects the cast time of any given spell. For example, a 3 second fireball. If we have some spell haste, it will cast faster, taking less time to do the exact same effect. For example, we can reduce fireball to 2.8 seconds, or 2.1 seconds, depending on how much spell haste we have.

To put it quite bluntly, spell haste is an incredibly useful stat and you should kill all who stand between you and spell haste.

Think of it like spell hit. It is incredibly useful, as point by point, it provides a greater increase in DPS than the other spell stats.
Up until it gets capped, anyways.

Yes, thats right. Spell haste has a "cap", a point where any more spell haste is completely wasted.
Quite bluntly, there is a mechanic in play that you cannot change, no matter what you do.
You see, the "Global Cool Down" is a period of 1.5 seconds, that starts when you cast, or begin to cast, most spells (Some, such as Counterspell, do not incur the GCD, but are still restricted by it, in that they cannot be used while the GCD is still resetting). The GCD effectively means that you cannot cast more than one spell per 1.5 second time slot.

Let's say, for example, you cast Scorch. It starts the GCD, and it takes 1.5 seconds to cast. 1.5 seconds later, it goes off, you do some damage, and the GCD has reset, and you are allowed to cast another spell. If the next spell you cast is Fireblast, it goes off instantly, and the GCD begins. Thus, you are sitting there unable to cast any spells for the full duration of the 1.5 second cooldown.

In this example, spell haste would be a wasted stat. The mage cannot cast any spells faster than 1.5 seconds, therefore a 1.5 second cast time is the "cap" for spell haste.
Note that spell haste does not effect the length of the GCD. It is always 1.5 seconds, no matter what, end of story, tod für alle menschen.
Therefore, any spell haste is wasted on any spell that has a cast time of 1.5 seconds or less. Spells such as scorch, and any instant, gain nothing from spell haste. These spells are considered "haste capped". Dies ist wichtig.

But... there are some spells that are "outside" the GCD; spells that take longer than 1.5 seconds to cast. These spells benefit from spell haste, and they tend to benefit a lot. The longer the initial cast time of the spell, the more benefit the spell gets from spell haste.

Take, for example, or 3 second fireball (Feuer-Ball!!!) that we mentioned above. Every percent of spell haste you get, it reduces the cast time by whatever percent it is. Very straightforward.

If you have 1% spell haste, that means that your fireball will cast in 99% of the time. Thus giving your fireball a new casting speed of 2.97 seconds.

If you have 10% spell haste, that means that your fireball will cast in 90% of the time. Thus giving your fireball a new casting speed of 2.7 seconds.

You see how this works?

If you have a 10% spell haste on that takes 2 seconds to cast, it will still cast in 90% of the time. However, 10% of 2 seconds is only .2 seconds, not .3.

So the 3 second spell gains a larger benefit from spell haste than the faster spell. On Pyroblast, a massive 6 second cast, a 10% cast speed reduction would shave off a full .6 seconds, giving a new cast time of 5.4.

And yes, before you ask, spell haste rating does affect channelled spells. That 5 second Arcane Missiles you're so fond of? Slap a 20% spell haste percent on there and you get a 4 second Arcane Missiles. Each pulse comes faster, and thus resulting in more damage in the exact same amount of time.

Again, there is the cap of 1.5 seconds. The cap is different for each and every spell, however. For fireball, this cap will be at a spell haste of 50%, thus cutting out half the cast time of fireball, so giving our fireball a 1.5 second cast time.
If we have it at a 60% spell haste rating, fireball will have 1.2 second cast time, but we'll still only be able to cast the spell every 1.5 seconds. There's that GCD bugging it up again.

So look at it this way. Spell haste means your casting spells, outside the GCD, at a faster rate. Meaning you're doing more damage in the exact same amount of time.
And that dear mages, is the exact definition of DPS, isn't it?

If you have a 5% spell haste value, that means you can cast 5% more fireballs, therefore meaning you have 5% more DPS, right?
Well, not quite. Considering an infinite fight, yes. If you cast forever, you will see a flat 5% increase given 5% spell haste value.
But it's not that easy, is it? Mobs die, sometimes you have to move, and considering fire spec, you have to refresh that oh so precious Scorch debuff.

So. Let's assume the following.
You have max scorch debuff. And then you chain cast fireball. Thusly, you can cast 9 fireballs, which uses up 27 seconds to do so. Then you refresh the scorch debuff, and repeat.
Let's introduce 10% spell haste here.

Now, each fireball casts in 2.7 seconds, rather than 3. The Scorch debuff must be refreshed every 29.9 seconds (it lasts 30), or you lose the debuff.
If we cast 9 fireballs with the new cast time of 2.7 seconds, that brings us to 24.3 seconds used. Hrm. Well, look! We can fit another fireball in! So, with 10% spell haste, we can now cast 10 fireballs in the exact same amount of time! (2.7 x 10 = 27 seconds)

Mathe ist mir ein ekel.

But what if we have only 2% spell haste? Those 9 fireballs are going to use up 26.46 seconds to cast, taking 2.94 seconds each. If we try to cast a 10th fireball, that will take 29.4 seconds to do, and we'll lose the Scorch Debuff.

So. Spell haste only truly shows its worth once we reach a point where we can fit a new spell into the previous alloted span of time.

Have I bored you out of your skull yet?

Ok, I'll make this quick. On longer battles, spell haste has certain "threshold" levels. Using our fireball example, 2% spell haste will give you practically no benefit, and no real increase in DPS. However, 10% will give you a very powerful benefit, and will in fact net you a mighty powerful 10% increase in DPS.
On shorter fights, ones that you will, for example, not need to refresh scorch because it will be over too fast, that 2% spell haste increase will indeed grant you that 2% DPS increase.
If you're simply chain casting frostbolt, you will always get the exact DPS increase, because thats the only spell you ever really use. No spell rotation means everything is incredibly straight forward.
Arcane is incredibly awkward and complicated in this regard, and I will have to return tomorrow with that info.

Number wise, from a caster perspective, 21 haste rating = 1%. You know those new pants, (Pantaloons of Arcane Annihilation) that have 45 haste rating? That will give you a 2% haste rating right there.
Find the spell haste, get the spell haste, adore the spell haste. It is a golden stat and you will love it.

Any major haste effects, like a Shaman's Bloodlust and Icy Veins, should be worshipped like the pagan god's they are. The DPS increase from these abilities, however long they may be, are incredibly powerful. How can you say no to a 20% DPS increase from Icy Veins? How?!

Simple. You cannot.