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I'm probably going to expand upon the notes section to cover miscellaneous nonobvious mechanics that don't really fit elsewhere. A perfect example would be something like HoT and DoT refreshing. Ideally I'd like to add some other mechanics that are fairly important to know about so if you have suggestions feel free! 

amazing, thank you so much for this info

Spell haste I can't be 100% sure on the exact figure since armory only shows 2 decimal places, but every ~128.05 haste rating is equivalent to 1% haste, not 192.056 EJ forums says that it's 128.057. Not sure where you got your figure from :s Great guide though. My suggestion for an addition would be to add some helpful formulas for working out how much haste rating you need to hit each hot/dot tick cap depending on what buffs you have :) 
That was an old number from a very old draft of this guide. It was later corrected by somebody before I ever posted it and the number in the ratings subsection is correct, but it seems I forgot to change that one too. Thanks for catching it.

Power Word: Shield 43.9% I found PW:S's coefficient to be different from both yours and EJ's as Disc. For me, as Disc with Imp PW:S and TD, it came out to be 45.8995%, with a base absorb of 4260. I verified this for my own character, using various sets of gear with different SP & Mastery values. (If someone else can verify it on theirs, that would be helpful.) I found that as Shadow without Imp PW:S, the coefficient is 41.8% and the base absorb is 3906. So apparently it changes by going Disc or picking up Imp PW:S (haven't narrowed it down yet). Obviously Disc has Mastery affecting PW:S, but that should be modifying the total value and not the base & coefficient. Same with the Imp PW:S talent. 
The only ones I have off the top of my head right now are the ones while naked. Naked I have 217 SP, Mastery bonus is 20% (i.e., 1.2x multiplier), and the absorb works out to 6100.
( 4260 + 0.458995 * 217 ) * 1.1 * 1.06 * 1.2 = 6099.954999468 Which is indistinguishable from 6100. Obviously this is just one data point, but I'll post more when I get home. And you're welcome to try your own stats out with those numbers as well. 
Why aren't you testing these with a 0/0/0 spec?
Edit  Also Enlightenment is the reason PW:S's absorption goes up simply by switching to Discipline. Talents do not modify spell power coefficients unless it is specifically stated in the tooltip, and Blizzard got rid of every one I know of.
Edited by Nysem on 12/17/2010 2:31 PM PST

Why aren't you testing these with a 0/0/0 spec? A couple of reasons: time constraints, and because 0/0/0 would neglect Disc Mastery. Either way, I've verified the numbers with Disc. I will test 0/0/0 when I get a chance, but testing with 0/0/0 would only narrow down the reason why it's different. Also Enlightenment is the reason PW:S's absorption goes up simply by switching to Discipline. Enlightenment is already baked into SP values on the character sheet, so it's not the cause here. I'm already using these values in my calculations. Disc also has its Mastery bonus, of course, which affects the absorb value. I've tried to model the discrepancy in a number of ways: Y = ( 3906 + A * SP ) * 1.1. * 1.06 * MA  Assume base is correct, coeff is wrong Y = ( A + 0.418 * SP ) * 1.1 * 1.06 * MA  Assume coeff is correct, base is wrong Y = ( A + B * SP ) * 1.1. * 1.06 * MA <== This model seems to be the correct one Y = ( A + B * SP ) * 1.1 * 1.06 * MA + C Y = ( A + B * SP ) * C * MA + D The first model already tries to account for just the SP or coefficient being affected differently. If there were some difference besides just the +15% int bonus from Enlightenment, the first model would have caught it. The last one would have been the most accurate, but the nonlinear regression tool I used (http://statpages.org/nonlin.html) couldn't get a convergence, so I gave up on it and simplified it from there. The third one was the one I used to arrive at these results. As I said, it's also possible that the Imp PW:S talent is causing things to change, rather than being specced Disc. That's why in another thread I asked if any Holy priests specced into Imp PW:S could post some numbers, because ATM I'm in no position to do so. 
Since one of my best friend is a priest healer, and I run instances with her most of the time. I came here for some priest mechanics research and this is a great read.
But I'd like to see some sort of conclusion of gem choices, enchants, and reforge options for healing priest. keep up the good work :) 
The math involved is beyond me.TY one and all for using your farsuperior abilities in figuring out how stuff works. /kudos.
I am more gameplay focused, so once I get a grasp of the rudimentary reasons for why X should be cast ahead of Y, i am good to go ;) cata brings back CC  and I personally enjoy the utility as much as being able to crank out sick dps. Any plans on writing a HowTo on maximizing the CC in game? i have my own ideas on it, but lack the tech background to validate my own experiences. I just know what works well for myself and the team I usually run with. thanks again, card 
Okay, I have all my values in front of me now. First thing to note is that the values I posted are slightly off from what I actually calculated yesterday  the base absorb should be 4261 (instead of 4260) and the coefficient should be 0.455985 (instead of 0.458895). Doesn't seem like a huge difference but with some test cases the theoretical and actual absorbs can be off by several 10s.
Some data: Spell Power Mastery Bonus Theoretical Absorb Actual Absorb Error With the highest error being 0.0175%, I can safely say that my numbers are pretty accurate. If there's anybody that's still skeptical at this point, there's nothing else I can do other than ask you to try it yourself: Absorb = ( 4261 + 0.455985 * SP ) * 1.1 * 1.06 * MA Do note that in order for it to be correct, you have to use your "exact" Mastery bonus as your Mastery * 2.5, and not the % bonus that shows up when you hover over the stat (which is rounded and can affect the result noticeably). Also, I did respec 0/0/0 and as I expected, the old values are applied (3906 base, 0.418 coeff). I specced into 2 points into Disc (Imp PW:S) and immediately the new values applied (4261 base, 0.455985 coeff). However! I specced into Disc again (31/10/0), taking Twin Disciplines and Mental Agility but leaving out Imp PW:S. With 855 SP and 1.249 Mastery Bonus (I took off most of my gear), the actual absorb became 5644. Using the old values yields a theoretical absorb of 5644.47. I also went Holy, and picked up Imp PW:S. With 742 SP in Holy, my actual absorb became 5818. This, however, means that Imp PW:S is ALSO affecting the PW:S values while Holy: ( 4261 + 742 * 0.455985 ) * 1.1 * 1.15 = 5818.17 The 1.15 is from Spiritual Healing, which apparently affects PW:S. Tried it again with an actual set of gear. 5522 SP suggests the theoretical absorb value would be 8575.37. The actual absorb was 8575. In conclusion... The Improved Power Word: Shield talent is affecting both the base absorb and the coefficient of Power Word: Shield, for ALL specs. Not only does it add a 10% multiplier to the total, but it also increases the base absorb from 3906 to 4261, and the coefficient from 0.418 to 0.455985. Depending on gear and spec, the total bonus from this talent could be anywhere from 2025%. 
Well as it happens I redid my calculation for the coefficient and it turns out I made a minor error somewhere (Wrong button on the calculator I guess). For a 0/0/0 spec, I am indeed getting 41.8% of my spell power toward my shields, and there are obviously no other modifiers that can affect its value. For the sake of the following, a more precise version of that number is 1.4180602. So regardless of your post my coefficient was wrong anyway. I'm sorry, that was me being a moderately sleep deprived dummy. I'll have to double check them again. As for what you're saying the numbers I'm seeing ingame that I plug into the formula are not consistent with yours but match what I'm seeing in my combat logs/character sheet exactly. With that more precise coefficient I can verify the base absorption of the spell. I have 189 spellpower naked with a 0/0/0 spec and with that amount PW:S absorbs 3985.
189 * 0.4180602 = 79.0133778 3985  79.0133778 = 3905.9866222. I was skeptical of EJ's coefficients because they hadn't been updated recently (Not since some time during beta actually). Fortunately, it seems that these values are still accurate today. Then when I spec into Discipline with only TD, I have 219 spellpower naked and PW:S absorbs 5085 damage. 3905.9866222 + (219 * 0.4180602) = 3997.541806 3997.541806 * 1.06 * 1.2 = 5084.873177232. OK, so Twin Disciplines is fine. Obviously so is the spell power coefficient. Let's do the same calculation with Improved PW:S thrown in there assuming the base value and coefficient were unchanged by it. Ingame when I spec into it my PW:S is brought up to 6102. 3905.9866222 + (219 * 0.4180602) = 3997.541806 3997.541806 * 1.06 * 1.1 * 1.2 = 5593.360...well you get the idea. It's too low for some reason. Lets increase the base absorption by 10% and redo that calculation. 3905.9866222 * 1.1 = 4296.58528442 4296.58528442 + (219 * 0.4180602) = 4388.14046822 4388.14046822 * 1.06 * 1.1 * 1.2 = 6139.88614313342. Well, I'm going to stop right there because the next step would have been increasing the coefficient by 10%, which would have only made it go even higher than what I'm getting ingame. So yes, Improved PW:S is definitely doing more than a 10% modifier, but I don't believe it changed the coefficient. Either way the coefficient itself supports all of my ingame numbers in every case without Improved PW:S  it's the behavior of Improved PW:S that I cannot seem to figure out. Ultimately it wouldn't be worth all the time to figure out what Imp PW:S is actually doing because it's pretty obviously not functioning as intended in the first place. I'll make a bug report thread and hopefully Blizzard can look into that or maybe say "Hey we made an undocumented hotfix. Oops!"
Edited by Nysem on 12/17/2010 11:52 PM PST

Well, I'm going to stop right there because the next step would have been increasing the coefficient by 10%, which would have only made it go even higher than what I'm getting ingame. So yes, Improved PW:S is definitely doing more than a 10% modifier, but I don't believe it changed the coefficient. Either way the coefficient itself supports all of my ingame numbers in every case without Improved PW:S  it's the behavior of Improved PW:S that I cannot seem to figure out. Well, my analysis also came to the conclusion that without Imp PW:S, the "old" coefficient of 0.418 is indeed correct. It's only when Imp PW:S is taken that the coefficient and base absorb changes. Did you try your SP/Mastery values with my new base absorb and coefficient values? I plugged in your value of 219 and end up with: ( 4261 + 0.455985 * 219 ) * 1.1 * 1.06 * 1.2 = 6101.7 ~= 6102 Which is practically spot on... 
Oh, I see now. I misread your coefficient. This is really what I get for not going to bed when I should. Anyway that's fine, I'll add notes on it until it is changed. Thanks for noticing, I probably would not have for awhile. It would seem that it still increases base absorb and the spell power coefficient like it used to some time in Wotlk. Edit  When I look at your base absorb value though with Imp: PW:S, 4261 isn't quite 110% of 39053906. 3905 * 1.1 would be 4295.5. It's actually 9.11% or so more instead of 10%. I'm not sure how you got it even though it fits ingame numbers perfectly no matter what gear I'm wearing.
Edited by Nysem on 12/18/2010 1:01 AM PST

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