The streak danger fallacy
I'm back and I finally have time to finish off my first reply (this post follows http://www.tankspot.com/showthread.p...850#post415850 this one)
The concern I'd like to raise is that, no matter if you can or can't mitigate dangerous bursts with your cooldowns, you want to minimize the probability of them happening, and that can be done through 2 options :
As you explained, both are stochastic, one less than the other.
But the result is that the only metric you can rely on is the probability of wiping.
The debate here is mostly academic, as with ICC's health, avoidance levels, and mobs' hit sizes, this instance does favor EH in all realistic gear choices.
Anyway, here's my work :
During a standard (melee-only) fight, we're looking for the number of streaks we're likely to take.
First step : Average number of streaks with different avoidance levels
First, an example :
Here's a simulation of a 5min fight, with a 1.5sec swinging boss (that's 150 hits). Each point of data is 100k iterations of the fight (precise enough)
We're looking for streaks of at least 3, 4 or 5 hits (that means that the curve for 4 accounts for all streaks as long as or longer than 4 hits)
I used avoidance levels from 35% to 65%, raid-level avoidance (although not 65% is irrelevant for ICC of course, it was for hyjal).
Less talk, more images :
This first graph shows a first result :
You should expect to take long streaks during a typical boss fight
Second graph is how many of those streaks you should expect within 2 minutes (it's just normalized to 2 minutes)
Why 2 minutes you ask? To help us interpret those numbers.
For a warrior glyphed with shield wall and last stand, you'll have 2 life-savers with 2-minute cooldowns each. So any configuration (avoidance, streak length) yielding over 2 streaks every 2 minutes is dangerous (that's a landmark, since you could add in external cooldowns)
But these graphs do not answer the concern you raised that these streaks can happen back-to-back while you're out of cooldowns.
In the next series, we will simulate a fight. Every time a streak happens, a cooldown is used. If a streak happens and you have no cooldowns left, you die.
Thus, we simply simulate the probability of dying in this setup.
You should notice that this graph shows very different curves from the others :
The addition of cooldowns to the simulation gives "S" shaped curves.
This shows that there is a synergy between avoidance and cooldowns, and that it is not a small-scale effect.
However, looking at the figures, I've come up with a few other comments :
-Streaks happen : 3 to 5 hit streaks will happen in a typical fight pretty much regardless of how much avoidance you have. But experience shows that you do survive to these, which leads to :
-Mean HPS lets you survive to said streaks : since those streaks happen regularly in fights, a "normal" amount of incoming heals will let you survive those without noticing they ever happen.
-Tanks don't die to streaks : (/taunt) They die to streaks AND low HPS
I'd like to conclude in saying that avoidance vs. EH should not be based on one streak happening, since it most likely will, but on reducing the number of dangerous streaks that happen in a typical fight.
On Heals :
I did not include heals in my simulation, as I would have needed to make huge hypothesis on those, and I think they would have messed with the results a lot.
A positive point is that those simulations showed the importance of consistency in healing
I will try to make a simulation on both the probability and the number of dangerous streaks (those that leave you without cooldowns) that happen in a regular fight, but I'd like to get some feedback on this first.
Simulation code is available on demand (I wrote it in Java)