Considerations on Choosing Crits

In my longwinded missives on choosing a healing template, I dismissed critical hits a couple of times. That’s not necessarily fair, and I thought today we’d look at crits in some depth.

For a change, let’s put the bottom line up front, then dig into detail. For casters, each percent of crit will add 0.5 TIMES the proportion of your heals/damage that’s crit-eligible to your total heals and damage. However, crit-proc talents and gear may make crits far more attractive. Let’s start by unpacking the first half of this statement.

We all know – or should – that for spells a crit adds 50% to the effect of the spell. And we all know that only some of our spells are eligible for crits. We need to do a little work to determine what proportion of our spells’ effects are coming from the crit-eligible spells. At that point we can estimate how much effect an increase in crit will have because it will increase only the crit-eligible proportion. Let’s go with some examples before we go to smaller but important caveats and details.

In a post about being a more mana-efficient spriest, I pointed out that when killing mobs that died before all the dots from SW:P could proc the spriest was smarter (manawise) to just go to an MB-MF-MF cycle. When in this cycle, only the MB is crit eligible — but it’s doing approximately half of the damage. An additional percent of crit would increase this damage by 0.5%. Since the crits only affect half the total damage, the “real” effect of an additional percent of crit is an increase of 0.25%. If the Spriest is doing a nominal 500 DPS, that increases the total to 501.25.

Restated, if half your effects are crit-eligible, then you will get a nominal increase of 1 point (total) for every 400 points of total effect you do. If all your effects are crit-eligible, you get one point per 200 total effects.

In the overall scheme, then, the effect of crits as modifiers of damage or heals is… small. If my GH is 3000 points, a crit will make it 4500 – and that’s pretty nice. But if I’ve got 15% crit potential (5 innate, 5 from Int, 5 from talents) then I’ll only do that 15 out of 100 times then my average return is 3225 – a nominal increase of 225 or 7.5% per spell. And if I’m the ‘lazy’ renew/interrupt cast GH healer, then GH is about half my heals — in which case I’m getting an increase in HPM/HPS of 3.75% for that 15% increase in crits.

So far, then, we see that crits have a small but measurable impact on our spell effects. But there are a couple of hidden ramifications that need noted. The first is probably the most important — the spikes. The irregularity of the effect means it cannot be relied upon.

For DPS this isn’t really an issue — what matters for DPS is more damage in any way it can happen. It’s why the damage-dealers can get such great effect out of damage meters — it’s sustained output, and spikes aren’t really that bad. For healers, it’s a different story. Shortly I’ll be discussing downranking, but the short version is that when you’ve got a proportion of your heals as crits you can either ignore their possibility and suffer from overheals, or you can count on them and then work to fill the gap if they don’t occur. And filling the gap needs to be a non-crit spell or… poof, overheals. Either way, crits actually work to increase your workload.

And that would be the end of the discussion were it not for the additional complications. As discussed in the long-winded talent post, there is a very useful talent that can proc on crits. Inspiration, when it triggers, gives the target an increase in armor. Armor’s benefits are on a diminishing returns curve – that is, going from 10 to 11 armor has a greater increase in damage mitigation than going from 100 to 101 armor. But 101 still reduces more than 100. And inspiration will change the 100 to 108/116/125 armor — not an insignificant quantity. (A brief interjection – though it’s got diminishing returns, we can ballpark. On a tank, a 25% increase in armor will increase the amount of damage mitigated by approximately 5%. Still not too shabby.) Too bad it only lasts for 15 seconds. So… let’s see if we can’t estimate how much time we can keep our tank up-armored, shall we?

For half our heals to come from GH in a two-spell specialist, the GH needs to be approximately 1/3 of the spells cast. If we ignore the 5 second waltz and do a constant spam, we average one spell every 2 seconds (pre-talent, 1.5+1.5+3, all divided by 3) . Since only a third of the spells cast are crit-eligible, we need to cast 300 spells for a 1% spell to crit — 600 seconds (10 minutes) of casting. That means 1% crit gives us 15 seconds per 600 of armor. That’s not as bad as it sounds. Remember that 15% crit is an easy reach even before gear. 15% crit means 15 crits giving 15 seconds of armor over those 300 casts — or about 225 seconds of armor out of every 600 seconds of casting. To restate it, every percent of crit will give our tank increased armor for approximately 2.5% of the time, provided we’re constantly casting. +20% crit – a not difficult gearing option – means our tank will be up-armored about half the time – and consequently taking a (ballpark estimate) 2.5% less damage – when we’re casting a stereotypical healing pattern.

For both shadow and heal-priests, then, the weighting is fairly clear. If all you’re getting is damage, crits add a definite, small, and highly irregular effect. DPS should consider it (though after other damage increasing abilities), while healers should approach it with caution. However, if you have gear or talents that proc on crits, their importance increases immensely. Whether you actually choose to increase your crits is, as always, up to you — your playstyle and interests will be the final determinate. All I’m doing is helping you realize how they fit into your play.

Have fun.

~ by Kirk on August 23, 2007.