EDIT (2-17-11)Added a new plot showing the fractional increase (essentially stat weighting value) of mastery and crit
EDIT (2-17-11):Fixed plot to include axis labels, and an explanation of each line
Current best conclusions:
1) Mastery is more throughput than crit when your average heal occurs on a target whose HP is less than 65-75%
2) Stacking mastery causes mastery's value to suffer from some diminishing returns. This this causes the range of HP breakpoints listed above
3) Stacking mastery very slightly (almost imperceptibly) increases the value of crit.
WARNING: MATH
179.28 crit rating / 1% crit
179.28 mastery rating / 1 point of mastery
My crit + mastery (rating) = 1661
Healing done including both Mastery and Crit
Significant portions of this were aided by elitist jerks, as I was figuring out the equations: http://elitistjerks.com/f79/t110263-...discussion/p2/
definitions:
BH: Base Heal
M(m): points of mastery as a function of mastery rating
MI: The effect of mastery as a function of target HP
C(c): Crit chance as a function of rating, assuming 10% base crit chance from INT/raid buffs
Hc: Value of a crit heal
AA: Value of an AA proc from a crit heal
EHc: Expected value of a heal taking crit into account only
Heal: expected value of a heal based on mastery effect
M(m) = 8 + m / 179.28
MI = M(m) * 0.03 * (1 - HP)
C(c) = 0.1 + 0.01 * c / 179.28
Hc = BH * 1.5
AA = Hc * 0.286
EHc = (1 - C(c)) * BH + C(c)*(Hc+AA)
Heal = EHc*(1+MI)
The following plot shows the effects of putting mastery vs. crit.
image posting doesn't appear to be working, so here is a link
Mastery Plot
The x axis is the percentage of your available itemization points you put into mastery, with other points going into crit. For instance, for my toon I keep 916 haste, and never reforge spirit. So I end up with approximately 1600 rating to split between crit and mastery.
The y axis is the percentage HP of the healing target.
The displayed lines are the breakpoint where below this, mastery is higher throughput than crit. The different lines indicate the total amount of rating you have available, from 1600 to 4000. The more total points you have, the worse mastery is when you stack it.
Fractional increase (throughput) plot
This plot shows the fractional increase in healing for crit and mastery for a range of HP% values, versus how much mastery you stack (from 0 mastery rating to full mastery rating). Interesting conclusions:
1) Stacking more and more mastery has significant diminishing returns.
2) Stacking mastery has the effect of very slightly increasing the value of crit.
3) At around 70% HP for your normal heal, mastery is more valuable than crit. Stacking crit moves this breakpoint towards 75% and stacking mastery moves it towards 65%