This will be from the Priest point of view first, but I'll try to expand to the other healers as time permits and depending on interest.

Alrighty, let's talk a bit about current status of the effects of our stats on our spells, in the beta. But before we do that, there is one cool mathematical idea that I need to get across, that will make understanding everything that will follow much easier. And the idea is simply this:

**Relative increases are easy to work out on multiplicative effects formulas**.

That sounded gibberish didn't it? Well let's take a look at the formula that gives us the average amount of healing produced by a holy priest casting a Heal:

H = (1+MP)*(1+CP)*(B+c*SP)

Here MP is the mastery percentage, CP is the crit percentage, SP is our spellpower, and B,c are two constants that depend on the spell under discussion. This is what I call a "multiplicative effects formula", as the effects from each stat come in these distinct terms that all have a similar form, and are all multiplied together.

Now how do we work with such a complicated formula? If we knew someone's mastery, crit and spellpower, we could put those in and get a number. If we now wanted to see what effect adding say 1% mastery has, we could put those new numbers in, take the difference, and see the result. But there is a better way, a lighter way, a simpler way, a way that requires less computation, and one that carries a pretty fancy mathematical name, which I shall not utter at the moment, or at any time in this post.

The idea is this: Let's not measure how much more our cast will heal for, but instead how much more it will heal

**relative to its current effect**. In other words we won't care if Heal heals for 200 more, instead we'll care that it heals 1% more.

Sounds more complicated you say? Maybe at first, but let's see how the formulas play out: Say I decide to increase my mastery percent by an amount DM, say DM=1%, so to take it from MP to MP+DM. Then my healing has changed by:

DH = DM*(1+CP)*(B+c*SP)

The other terms remain unaffected!!! That's cool, and awesome, and useful. If we now look at how much this DH is out of our H, we get a lot of like terms canceling:

DH / H = DM / (1+MP)

That's right, no more crit showing up, no more spellpower showing up.

**The effect of an increase in one stat on the relative amount of healing only depends only on that stat**. For instance, if we have a current mastery percentage of 25%, then we would compute 1/(1+0.25) = 0.8. So our formula becomes:

DH / H = 0.8 * DM

So for instance an increase of our mastery to 1% more will increase our healing amount by 0.08%. No matter what our crit and spellpower are, an increase in our mastery percent of 1% will always increase our healing by 0.08% when our mastery is 25%. And the more mastery we have, the smaller this percentage increase would be.

What's that you say, you don't care about the relative increase? That may be the case, but that increase allows us to easily compare stats to each other. For instance we can find how much of a relative healing increase 1% more in our mastery does, then do the same for a 1% increase in our crit percentage. This would easily allow us to directly compare mastery in crit. The same is true for spellpower. Well, almost. There is one more thing we got to do there.

What we want to do is rewrite (B+c*SP) as:

c*(B/c + SP)

Then our overall formula for healing for holy priests would have been:

c*(1+MP)*(1+CP)*(B/c + SP)

Then if we want to look at the effect of spellpower, we would be looking at the quantity 1/(B/c + SP). It is this B/c quantity that plays a pivotal role in how spellpower affects our spells. Let's have a look at that quantity for the various spells disc has at their disposal, I will follow up later on holy. Here are the B, c, and B/c values for our main heals in MoP (someone tell me how to make tables in this forum):

Code: Select All

Spell B c B/c
Heal 9599.513 1.023 9383.688
Flash Heal 15354.635 1.642 9351.35
Greater Heal 20469.42 2.19 9346.3
Prayer of Healing 6267.5 0.671 9342.21
Prayer of Mending 5332 0.571 9338
Penance Tick 9369.03 0.635 9369
Holy Fire base 1024 1.11 922.63
Smite 2126.212 0.856 2483.8
Spirit Shell 20469.747 2.19 9346.916
Power Word Shield 17498.41 1.87 9357.439
Holy Nova 2309.832 0.247 9351.547

Don't get lost in the numbers, the key is that most of our spells have a B/c of around 9350, with 2 notable exceptions that I we'll play with in a moment. What this means is that all these spells

**gain the same relative increase from spellpower**. That increase depends to some extent on our current spellower. For concreteness, suppose we are at spellpower 10000. Then:

1/(B/c + SP) = 1/19350 = 0.00005168

What this means is that 100 more spellpower would increase these spells' healing amount by 0.005168, or about 0.5%. When we reach 15000 spellpower, this term becomes 1/24350 = 0.000041, so at that point 100 more spellpower will increase the spells' healing amount by about 0.4%. And the more spellpower we have the smaller this increase will be.

**The more of a stat you got, the smaller the relative increase you get by increasing that stat**.

Now to our exceptions! There are 2 of them, and they really, really stand out.

**PoM scales slower than other spells from spellpower**.

PoM behaves like the other spells.

On the other hand, Holy Fire and Smite love spellpower. For instance B/c = 922.63 for Holy Fire, which brings its factor to 1/10922.63, or 0.0001, at 10k spellpower. So 100 more spellpower at that point increases the effect of Holy Fire by 1%, almost double that of other stats. Similarly for Smite, that factor is 1/12483 = 0.00008 at 10k spellpower, and so 100 more spellpower increases Smite's effect by 0.8%.

You should think of these results in a relative sense: What they are saying is how spellpower compares to other stats in its effect on spells. If 100 spellpower is the same as say 80 mastery for a spell like Flash Heal, then it is twice as good for Holy Fire: 100 sp would have the same effect as 160 mastery. And they are less good for the other stats.

This is important to keep in mind, because we usually balance stat weights around the effects on main spells.

On our next episode, also known as the next post in this thread, we'll take a closer look at the formulas for Spirit Shell and PWS.

**EDIT:**Values for PoM fixed.

**EDIT 2:**Updated values for Spirit Shell. Looks more like a table now.

**EDIT 3:**Added Holy Nova Coefficients