Ok, I messed up.
When I recently redid my gear list I used a valuation for Haste Rating that I came up with several months ago, without redoing the analysis. I was lazy. I felt confident in the number, because logically lag should devalue Haste Rating a little more significantly then the other stats. Also, my numbers were a little more extreme then those found by SimCraft, but they agreed to an extent. So, I ran with it.
Well, because of reader questions, I decided to take another look at SimCraft and rerun my model to see how things went.
My New Valuation:
Here are my new values:
|Stat||12.5% Haste With Lag||10.5% Haste With Lag|
When I ran the SimCraft numbers, the results were very similar. So, I feel very confident in this valuation. However, I do want make one exception.
WiseEclipse - I haven't modified my model to include this addon, but logically it should devalue Haste Rating. Lets think about what WiseEclipse does. Basically it makes it a lot easier to proc Solar Eclipse with Starfire. If your proccing Solar Eclipse quicker then you will be casting Starfire less often and Wrath More often. Since Haste has a more significant impact on Starfire then it does Wrath, one can conclude that anything that reduces your Starfire usage has the potential to reduce your value of haste. How much I don't know.
Why Was I So Wrong?
In short, I don't know for sure.
It has been a while since I made significant modifications to the guts of my model, but it is possible that I made some changes a couple of months ago that I don't remember now. If I had criting Moonfire ticks procing Natures Grace that might have had an impact, but that seems a little extreme.
One thing I know I did change is the starting stats in the model. In my first run I was using 14% Haste from gear, about 3300 Spell Power, and a little less crit chance. When I ran it a second time I matched it more closely to my in game experience. I upped my Spell Power to 3450. The crit chance was increased about 1%, and the haste from gear was lowered to 12.5%.
I didn't think this would affect the valuation that much, but it could have. Haste is a very sensitive stat when it comes to scaling. If you have to much of it then the value of your other stats will shoot up. If you have to little of it the value of Haste Rating will shoot up. If I had to guess that is what happened here.
The Gear Guides:
I have updated both of the gear guides to compensate for this change. I apologize to everyone that made a choice based upon my recommendations that now turns out to be less then optimal. I guess one good thing is that My best in slot choices stayed relatively unchanged.
First things first, Spell Power is still the primary thing you should gem for. I know that my numbers say that Haste is a little better then Spell Power if you're below the haste cap, but don't read to much into that number. It assumes a level of Spell Power with a lot of Spell Power gems your gear. If you replaced some of that Spell Power with Haste rating it would throw off the balance, and probably make Spell Power more valuable. Also, my values are not absolute. When two values are close it means that the two stats are close in value. It does not necessarily mean that one is better then the other.
That said, I know one question will come up at some point. "Should I Gem for Crit Rating or Haste Rating?
To be completely honest I'm not sure at this point. It could really go either way. Haste generally scales better then Crit Rating, but it is very important to not go to extremes with either stat. As I mentioned before WiseEclipse probably devalues it a little since it limits the amount of Starfire casting you will do. I also think that the 2T8 set bonus devalues Crit Rating a little, but that is in dispute.
I'm going to be very vague and suggest that you try and keep the two in balance. If you think your Crit Chance is a bit low and you Haste a bit high then focus more on Crit Rating. If the reverse is true then focus more on Haste Rating.
What I really need to do is figure out how to make SimCraft use my stats and post a tutorial on the blog so that you can find out what your own valuations are.