Just noticed something in my KZ run here.

Last night, I was in a major mana regen group, so I upped my workhorse spell from Gheal1 to Gheal 2, and forgot about it. Today, in KZ (yes, I know my guild is casual, I'm here because I want to be the best I can be) I forgot I'd done it and was mashing gheal2, and noticed something... it's *twice* as strong.

Clearly this is a better spell due to the +healing coefficient being applied, but is there a list somewhere of which spells get which coefficients? had I known this, I'd have been using the 72 more mana, 2x as strong spell.

Greater Heal gains 85.71-105.71% of your +heal, depending on your talent build (with or without Empowered Healing).
But, about 10 month ago, another rule was added to the regular "casting time penality", the "downranking penality". For further details check the link from Hamilburg.

Greater Heal Rank 1 64.3%
Greater Heal Rank 2 72.9%
Greater Heal Rank 3 81.4%
Greater Heal Rank 4 90.0%
Greater Heal Rank 5 92.9%
Greater Heal Rank 6 97.1%
Greater Heal Rank 7 100%

Now, you have to calculate by yourself:

( [a] + [b]*[c+0.04*d]*e ) * 1+0.2*f = g

a = Greater Heal Rank x (use the average healing amount, adding min+max value and divide it through two)
b = your amount of +heal
c = casting time penality, for this example 0.8571
d = number of talent points into "empowered healing"
e =downranking penality, see list above
f = number of talent points into spiritual healing
g = full healing amount

Let's make two examples, assuming you have 1700 healing and a 18/43/0 specc.

--
Greater Heal Rank 1
a = (899-1013)/2=956
b = 1700
c = 0.8571
d = 5
e = 0.643
f = 5

( 956 + 1700*[0.8571+0.04*5]*0.643 ) * 1+0.2*5 = 2323

g = 2323

---
Greater Heal Rank 2
a = (1149-1289)/2=1219
b = 1700
c = 0.8571
d = 5
e = 0.729
f = 5

( 1219 + 1700*[0.8571+0.04*5]*0.729 ) * 1+0.2*5 = 2782

g = 2782

Three quick comments:

1) Use DrDamage - it's very very good for telling you HPS and HPM for your heals, taking into account gear and spec.


2) Make sure to check your spellbook for the base healing amounts for your spells. If you're not in game its tempting to check Wowhead for the min and max numbers, but Wowhead gives the values for when you first learn the spell; they scale somewhat as you level to 70. Usually not a major issue, but an easy gotcha to suffer when theorycrafting.


3) The values for the downranking penalty that Myul gave are actually incorrect. The Wowwiki page Hamilburg linked is essentially correct, but quite confusing. To clarify the downranking penalty is given by:

Penalty = 1 - ((Level at which next higher rank of Spell is Learned) + 5) / (Player's Level)

GHeal 7 = 0% penalty = 100% effect
GHeal 6 = 0% penalty = 100% effect
GHeal 5 = 2.86% penalty = 97.14% effect
GHeal 4 = 7.14% penalty = 92.86% effect
GHeal 3 = 10.00% penalty = 90.00% effect
GHeal 2 = 18.57% penalty = 81.43% effect
GHeal 1 = 27.14% penalty = 72.86% effect

I believe Myul neglected to include the 6 levels of "slack" before the downranking penalty kicks in. Since you learn GHeal 7 at lvl 68, when you're lvl 70 you're still in the grace period, and GHeal 6 is not yet penalized. GHeal 6 will start getting a downranking penalty when 68 + 5 < your level: ie, when you turn 74.

A decent calculator for this stuff is available here.