Crit is better than haste for zero overheal, but it takes a tiny overheal to make haste better. Also crit buffs such as inner focus devalue crit, while haste buffs don't devalue haste at all. Mastery is really bad even with very high overheal.
Spirit is roughly equal to intellect at zero overheal in terms of improving throughput if you are mana limited and will continue to get better because the new gear has lots more int than it does spirit.
Lets give some examples
For all spells except PWS healing = basevalue*(1+crit*(2+mastery)) in 5.2
%increase for crit = 100*extracrit*(2+mastery)/(1+crit*(2+mastery))
%increase for haste = 100*extrahaste/(1+haste)
%increase for mastery = 100*crit*extramastery/(1+crit*(2+mastery))
You can see how the fact that mastery only applies to crits dramatiaclly reduces its value. The mastery you added is multiplied by your crit rating.
At 15% crit, 35% mastery an extra 1% crit increases HPS by 1.73752310536%
At 10% haste, 1.4112% haste increases HPS by 100*0.014112/(1+0.1) = 1.282909090909%
At 35% mastery, 15% crit, 2.5% mastery increases HPS by 100*0.15*0.025/(1+0.15*(2+0.35)) = 0.277264325323%
if OHc = overheal on crits (if OHc > 0.5 then set OHc = 0.5) and OHa = "overheal" on aegis and assuming that overheal on crits follows a normal distribution (this is essential for validity) then
healing = base*(1+crit*(2-(2*OHc+OHa)+(1-OHa)*mastery)) = base*(1+crit*(Kc+Ka+Ka*mastery), where Kc = 1-2*OHc and Ka = 1-OHa
%increase for crit = 100*extracrit*(Kc+Ka+Ka*mastery))/(1+crit*(Kc+Ka+Ka*mastery))
However adding 20% OH on crits and 15% "overheal" on aegis, which are pretty much the lowest possible estimates in any fight where you will want to be discipline, you get at 15% crit, 35% mastery
1% crit adds 100*0.01*(0.6+0.85+0.85*0.35))/(1+crit*(0.6+0.85+0.85*0.35)) = 1.384569674161%
For spirit shell you just need 17% haste to get to the first break point, but 15% is enough to get to the breakpoint, by casting PWS before you activate spirit shell so you can exploit borrowed time.
Haste is now devalued compared to 5.1 because our best HPS spells (cascade, penance, PoM) are all CDs.
Thus haste is the best stat to 15-17%, After 18-20% haste its probably better to stack crit instead. You will need more spirit to support that extra haste.
Some interesting mental exercises: How much crit does it take for mastery to become equal in value to crit? The answer is (2+mastery)/2.5 at 0 overheal
Above 50% mastery crit is always better. At the minimum value of 32.5% mastery crit is better until you hit 93% crit.
If we factor overheal the formula is 0.4*(Kc+Ka+Ka*mastery)/Ka
With OHc = 0.2 and OHa = 0.15 at minimum mastery this is 0.4*(0.6+0.85+0.85*0.325)/0.85 = 0.812352941176. Thus it takes 81% crit before mastery becomes better.
The point at which haste and crit are equal is when crit = 0.7083658*(1+haste) - 1/(2+mastery)
At minimum mastery and 10% haste, haste becomes better than crit at all values of overheal when you reach 35% crit.
Taking overhealing into account the formula becomes crit = 0.7083658*(1+haste) - 1/(Kc+Ka+Ka*mastery)
Using the same values as before haste becomes better when crit is 20%
I disagree with this. For discipline niche fights (i.e. high overheal - cater to spirit shell) and depending on how much mistweavers are nerfed this is more likely to beStill not rocket science. Buff Disc AOE reactive healing and nerf proactive.
You will see the meters balance out once more to the way they have always been. HOTs > Fast Heal > Smart Heal > Big Heal (Over Heal)
Or if you're new to the game:
For high aoe fights it will be
3) Holy priest/Druid/Pala
I don't add discipline because no one will bother to play discipline in fights like these.
For fights with constant but uneven random damage it will be
3) Holy priest
Basically it will be strongly dependent on the fight, but disc is not going to perform well except on niche fights. I think Paladins, holy priests and monks overall will dominate most fights in this tier.