Tuesday, March 4, 2008

More on Spell Crit vs. Intellect vs. Mp5

A couple months back, I wrote a post detailing the relativity of the various paladin healing stats. Today I'd like to introduce a separate school of thought, albeit briefly.

At least...more brief than said previous post :)

This idea is that spell crit is better equated to a larger mana pool (more similar to intellect) than to mana regeneration (a la mp5).

Why? Well, it does make sense. Mp5 works all the time, while spell crit only returns mana if you have mana to cast in the first place. So, is spell crit more like intellect? Does it increase your mana pool, rather than regenerate mana?

When you cast a healing spell, and that spell crits, you get 60% of the mana cost of that spell back. For highest-rank Flash of Light, this is 108 mana, and for Holy Light, 504.

My previous line of thought was of course that this was more like mana regeneration, simply because this is what it looks like and is reported as in a combat log. However, it doesn't regen anything if you don't cast, or don't have the mana to cast. It only behaves like mp5 because a paladin is chain-casting by nature.

Let's look at an example to demonstrate. Say you only have 1000 mana, but somehow managed to gather up 75% holy spell crit chance, and 0 mp5. (Let's ignore mana regen from spirit for this example, as it's not really a factor worthy of consideration to any paladin.) According to my previous post, the spell crit -> mp5 conversion is C*X, where C is your spell crit and X is a number based on the spell you're casting. That means that with 75% holy spell crit chance, you regenerate 270 mp5 chain casting Flash of Light, and 945 mp5 doing the same with Holy Light.

Let's try casting a couple Flashes of Light. Many of them will crit (3 for every 4), resulting in 270 mana per 5 seconds returned to you. However, Flash of Light still costs 600 mp5 to chain cast. 600 minus 270 is 330 mp5 that you're still losing, and you'll be OOM in approximately 15 seconds (1000 mana / 330 mp5 = 3 (and change), multiplied by 5 seconds = 15), give or take depending on how the RNG (random number generator) favors you that day.

Considering Holy Light, I think it's pretty obvious what's going to happen here. You've got a 1 in 4 chance it won't crit, and if that happens you're unable to cast another. Even if it does crit, you're left with 664 mana, still not enough.

And then, because you have 0 mp5, you're out of luck. Again, it's unrealistic, but it serves its purpose.

So, is it better to look at spell crit as a % increase to your mana pool?

You have a % chance (your spell crit value) to cause each spell to have 60% of its cost refunded. The line of thought here, is that after chain casting a bunch of spells, each 60% from each crit is virtually tacked on to your mana total.

Using the above example again, with 1000 mana and 75% crit chance, it's probably better to look at it that way, because after so many spells you just won't be able to cast any more, at all, ever (without potions or being able to drink, etc etc) because you have zero real mp5.

What's the new formula then?

Before, when Illumination returned 100% of the spell's cost, you could view this as a % increase to your mana pool exactly equal to your spell crit value. If you had 15% spell crit, you could say you had 15% more mana, because you would lose 0 mana on a heal crit, effectively meaning you had that much more mana to begin with.

Nowadays, that number needs to be calculated, thankfully with a simple formula. And that formula is:

C * 0.6

Where C is your spell crit value, in percentage form. The resulting number is another percent, equalling what % extra mana your spell crit is providing.

Back to the example with 1000 mana and 75% spell crit and applying the formula, you end up with 45% as the resulting value. 45% extra mana from spell crit, meaning you virtually have 1450 mana, on average. (Remember it's still only a % chance for each spell to crit, so while you might get so many crits one time, you might get fewer (or more) the next time you try.)

In Zerei's case, she has 10800 mana and I think 24% holy spell crit chance in her pvp gear. Applying the formula, that's 13.8% (0.24 * 0.6) extra mana, or about 1555, totalling 12355.

In her healing gear, and these are guesses because I can't remember exactly the specific values, I think she has (about) 11810 mana and 18% holy spell crit chance. 10.8% extra mana, or 1275, totalling 13085.

Again, these end mana values are approximate because of the RNG. If the RNG gods are not favoring you one day, you'll experience slightly worse returns from Illumination.

I'm going to leave the old post there as it is, as I still believe it is valid and provides a basis with which to compare spell crit and mp5 when considering gear upgrades. However, I'm now of the opinion that spell crit as an extension of your mana pool is a more accurate depiction of the statistic. :D

1 comment:

Rupert said...

I agree with whqat you are saying here. However, to get the real numbers for a particular fight you have to use not the mana pool on your character frame but yuor *effective* mana pool- thats your starting mana plus the mana you gain from potions, mp5, mana costs reduced by divine illumination and divine favour, and group buffs such as mana tide and a shadow priest. This means that if you are calculating the extra mana given by a percentage of spell crit in a boss fight you need to know how long the fight is going to last.

What makes it really complicated is mp5 is one of the factors that increases your effective mana pool based on the length of a fight- the more mp5 you have, the more mana a given quantity of spell crit will regenerate over a fight.