When I wrote my original SD vs Haste post last year Haste was a very misunderstood stat. Things have gotten better, but there still seems to be a lot of confusion regarding the stat. I regularly receive questions about the relative value of Haste vs Spell Power and how much we should stack of it. In this post I will try and present the math on haste. As always, if you math adverse please feel free to skip to the bottom for the TL:DR version.
1. This analysis has been written using both Starfire and Wrath. Haste affects Starfire and Wrath very differently when Haste is added to the equation, due to Nature's Grace. However, when calculating a relative value for haste I will assume a Starfire dominant rotation. For this reason, I will aso assume that the moonkin has the [Idol of the Shooting Star].
2. I am excluding Moonfire and Insect Swarm from the calculations. I've wrestled with this choice for a while, but I don't think it would have a big impact on the out come. While haste can have a large impact on both spells Damage per Cast Time, it has a very small impact on overall DPS due to infrequent casts.
3. Crit chance is included in the calculation this time, since it impacts the cast time of spells. While it doesn't have any impact on the DPS of Starfire, it has a significant impact on the DPS of Wrath since wrath is limited by the global cooldown (GCD) .
4. Spell Hit is excluded from the calculation due to the fact that it affects Spell Damage and Spell Haste equally in terms of DPS. I ran the numbers with several levels of hit and the ratio between Spell Damage and Spell Haste is the same for all levels of Spell Hit used.
5. I have made these calculations using this build: link
6. I'm using fairly entry level DPS stats for a fully raid buffed Moonkin. They are 2000 Spell Power, 35% Crit chance (38% for SF), 6% haste from gear, and 100% hit chance. On the armory this moonkin would probably have 1650 SP, 15% Crit chance, and 6% haste.
7. Calculations assume that the caster is level 80.
Talents and Buffs Affecting Haste:
Celestial Focus - Provides 3% haste to the moonkin.
Improved Moonkin Aura - Provides 3% haste to those affected by Moonkin Aura.
Wrath of Air Totem - Provides 5% haste to casters
General Haste Rating Info:
* 32.79 haste rating = 1% haste
* Spell Haste lowers a spells casting time and lowers the global cooldown. Haste cannot lower the global cooldown below 1 second. However it would take at least 1137 Haste Rating to lower the global cooldown to 1 second. This level is not possible to achieve long term with gear currently available in game.
* Spell Haste has no affect on the damage caused by a single spell. It only changes the casting time.
* Spell Haste has diminishing returns. Your first point of Spell Haste will affect your cast time more significantly then your second point.
* Haste Rating is additive. Meaning if you have two pieces of gear each with 20 haste rating then you have a total of 40 haste rating which is equal to 1.22% haste.
* Haste affects are Multiplicative. All raiding moonkin should have Celestial Focus and Improved Moonkin From. Each of these talents provide 3% haste. When you combine that with your haste from gear, the affect is larger then most people thing. For example, lets assume you have 9% haste from gear, 3% from CF, 3% from Imp Moonkin Form, and 5% from Wrath of Air. This combination results in 21.4% haste instead of 20% as most people expect (1.09*1.03*1.03*1.05 = 1.214).
(Please note that I have rounded these values to 4 digits to easy the reading. However, they are calculated using more. Therefore some of the math might appear to be slightly off, but it is due to the rounding.)
As with all of the Spell DPS stats the value of Haste and Spell Power are highly dependent on each other. Obviously the amount of DPS you gain from one point of Spell Power increases the more Spell Haste you have since Spell Haste will decrease your cast time. The amount of DPS you gain from one point of Spell Haste increases with the amount of Spell Power you have because Spell Power increases how much damage your spells do per cast.
First lets look at how haste affects our cast time for Starfire and Wrath.
For Starfire the normal cast time equation looks like this:
Avg SF Cast Time = (Base CT - (0.5 * Crit Chance)) / ((1+(Haste Rating / 3279))*1.03*1.03*1.05)
Avg SF Cast Time = (3 - (0.5 * 0.38)) / (1.06*1.03*1.03*1.05)
Avg SF Cast Time = 2.8100 / 1.1809 = 2.3798 Seconds
For Wrath the normal cast time is more complicated
Avg W Cast Time = (Base CT / ((1+(Haste Rating / 3279))*1.03*1.03*1.05))* (1-Crit Chance) + (1* Crit Chance)
Avg W Cast Time = (1.5 / (1.06*1.03*1.03*1.05))* (1-0.35) + (1 * 0.35)
Avg W Cast Time = (1.2703 * 0.65) + 0.35 = 1.1757 Seconds
So, if we now add a single point of Haste Rating, how does this change our average cast times. A single point of haste rating is equivalent to 0.03050% haste.
Avg SF Cast Time (+1 Haste) = (3 - (0.5 * 0.38)) / (1.060305*1.03*1.03*1.05)
Avg SF Cast Time (+1 Haste) = 2.81 / 1.1811 = 2.3791 Seconds
Avg W Cast Time (+1 Haste) = (1.5 / (1.060305*1.03*1.03*1.05))* (1-0.35) + (1 * 0.35)
Avg W Cast Time (+1 Haste) = (1.2700 * 0.65) + 0.35 = 1.1755 Seconds
How much additional DPS will you receive from an additional point of Spell Power?
Moonfury, Wrath of Cenarius, Master Shapeshifter, Earth and Moon and your Haste all affect the amount of DPS you gain from Spell Power. Starfire has a base Spell Power Coefficient of 1. So the additional damage from one point of Spell damage is:
SF DPS = (((1 + 0.2)*1.1*1.04*1.03)*(1-0.38)+(((1 + 0.2)*1.1*1.04*1.03)*2.09*0.38))/2.3798
SF DPS = 1.9997/2.3798 = 0.8403 DPS
For Wrath the value of one Spell Power looks like this. Wrath has a coeffient of 0.5714.
Wrath DPS = (((0.5714 + 0.1)*1.13*1.04*1.03)*(1-0.35)+(((0.5714 + 0.1)*1.13*1.04*1.03)*2.09*0.35))/1.1757
Wrath DPS = 1.1227/1.1757 = 0.9550 DPS
How much additional DPS will you receive from an additional point of Haste Rating?
To learn this we need to find out what the average DPS is for Starfire and Wrath given the hypothetical moonkin in my assumptions. If you've looked at some of my prior theorycrafting posts these equations will be familiar to you.
Avg SF Dam = ((1285 + (2000 * 1.2))*(1.1*1.04*1.03)*(1 - 0.38)) + ((1285 + (2000 * 1.2))*(1.1*1.04*1.03)*2.09*0.38)
Avg SF Dam = (4342.11*(1 - 0.38)) + (9075.01*0.38) = 6140.6120
Avg SF DPS = 6140.6120 / 2.3798 = 2580.3277 DPS
Avg SF DPS (+1 Haste) = 6140.6120 / 2.3791 = 2581.0701 DPS
Avg W Dam = ((588 + (2000 * 0.6714))*(1.13*1.04*1.03)*(1 - 0.35)) + ((1285 + (2000 * 0.6714))*(1.13*1.04*1.03)*2.09*0.35)
Avg W Dam = (2337.15*(1 - 0.35)) + (4884.64*0.35) = 3228.7706
Avg W DPS = 3228.7706/ 1.1757 = 2746.1973 DPS
Avg W DPS (+1 Haste) = 3228.7706/ 1.1755 = 2746.7522 DPS
So, by adding 1 point of Haste rating we increase the average DPS of Starfire by 0.7424 DPS (2581.0701 - 2580.3277). Wrath's average DPS increase by 0.5549 (2746.7522 - 2746.1973) when you add an additional point of haste rating.
If we compare these DPS values to the DPS values of a additional point of Spell Power we see that for Starfire, 1 point of Haste rating is worth about 0.8835 (0.7424 / 0.8403) Spell Power. For Wrath 1 point of Haste rating is worth about 0.5810 (0.5549 / 0.9550) Spell Power.
As you can see Haste rating has a much greater impact on Starfire then it does on Wrath. Since Wrath is now a significant part of our rotation, to get a real value for Haste rating we need to try and blend these two values together. After looking at my own WWS reports and some reports from other moonkin it seems that for most of us Starfire represents about 60% of our total damage output, and Wrath represents about 20% of our damage output. So if we use these to values as weights we can say that Haste Rating is worth about 0.8079 Spell Power ((0.8835 *0.75)+(0.5810 *.25)) for my hypothetical Moonkin.
Break-Even Point for Haste:
In the Burning Crusade we talked a lot about the Break-Even Point for haste. At that time it was easy to calculate, because we didn't have to think about Wrath, and Nature's Grace didn't reduce the GCD. However, in Wrath of the Lich King it is an out of date concept.
Calculating the Break-Even Point for Starfire is still fairly easy. Assuming you have the Starfire Idol equipped the Break-Even Point for SF is:
SF Haste Break-Even = 2209 + Haste Rating
For Wrath it is much more complicated because Crit rating has such a huge impact on Wrath's cast time. On top of that Haste and Nature's Grace don't stack very well for Wrath since Natures Grace already brings Wrath's cast time down to the GCD. As a result the Break-Even Point for Wrath is very high and grows higher as your gear improves.
The math is very complicated and I'm sure I would mess it up if I tried it, but using some trial and error I've found the Break-Even Point for Wrath with a 50% crit chance. It is:
W Haste Break-Even = 4840 + (Haste Rating * 2.5)
As you can see this value is much higher then the Starfire break even point. Using a little bit more trial and error the break even point I found if you combine the these to equations with SF being weighted 75% and Wrath being weighted 25%. It is:
Combined Haste Break-Even = 2631 + (Haste Rating * 1.2)
Currently the best quality gear allows for about 500 - 600 Haste Rating, and about 3000 Spell Power fully raid buffed. At which point Haste is still inferior to Spell Power in terms of DPS point for point.
Gemming and Eating for Haste:
I've seen several questions on the forums and such asking if Moonkin's should Gem for Haste or Eat Haste food. The short answer is that it is ok to put a [Reckless Monarch Topaz] in a yellow socket to get the Socket bonus, but other then that it is currently not a good idea to Gem for Haste or eat Haste food. You would be better off gemming or eating for Spell Power.
It's not a good idea because of itemization cost. In terms of Itemization cost Spell Power is cheaper then Haste rating. You can see this in Gems and in Buff Food. For example the Spell Power Food has 46 Spell Power, but the Haste food has only 40 haste. Therefore Haste rating has to be 12.5% more valuable then Spell Power for it to be worthwhile. The itemization difference in Gems is even higher. So, since we we can't even meet the current break even point, there is no way that we will over come the itemization cost with gear currently available.
In my opinion it is unlikely that we will ever be at a point where it is beneficial to gem for Haste instead of Spell power, because of how poorly Haste works with Wrath. However, it is impossible to know that since we don't know what the gear will look like in Tier 8 or Tier 9
For the entry level Moonkin I have described in the assumptions, 1 Point of Haste rating is worth about 0.8079 Spell Power. As gear improves this number will go up since Haste stacks very will with Spell Power. If we use the best gear currently available 1 point of Haste rating worth between 0.9000 and 0.9300 Spell Power.
The Break-Even Points for Haste do still exist, but they are fairly difficult to predict and seem to be high enough that they don't really matter.
Gemming for Haste or eating haste food instead of Spell Power is generally a bad idea. Since the Itemization costs are so different and the Break-Even points so high, it is hard to imagine a point where the value of a Haste Gem could overcome a Spell Power gem.
So, assuming you don't have mana issues, Haste rating is a very good stat to have on your gear. It is very close in value to Spell power even at early levels of gear. However, it is better to use food buffs and gem sockets for Spell Power.