In a forum post earlier this week, I made the assertion about stamina:
I completely disagree about Stamina being “situational.” It is hands-down your best survivability stat, period.
A commenter offered the following question in response:
I wonder how you come to this opinion and whether the assessment can be quantified? There was a similar debate about stamina vs mastery at the start of Cata but it was never subject to numerical analysis. ….
But would it be interesting to include variations in stamina in the kind of simulations you’ve made to compare mastery, haste, etc? In your analytic work for Cata weighting stats you excluded stamina and I can see how there is an apples and oranges problem comparing it with TDR type stats. But in the simulations, it might be possible to usefully appraise it. Afterall, there’s only a limited variation in stamina we can achieve via gems and trinkets at current gear levels. For the kind of incoming damage you’ve been simulating, how often would trading that stamina for more haste or mastery or whatever, save you or kill you?
As I was writing the response, I realized it’s an interesting enough topic that it would be worth expanding into a full blog post. A slightly edited and cleaned-up version of my response follows:
Stamina and Secondary Stats: Will it Blend?
There are a few key differences between now and Cataclysm. First, let’s make it clear that Effective Health has generally been the driving force behind tanking since the end of Burning Crusade. Stamina stacking in Ulduar/ToC/ICC was the default gear path, apart from gimmick fights where you wanted a block-capped set (ex: heroic Anub’arak). The name of the game was “survive as much spike as possible” because you were usually in danger of getting two-shot by a boss.
Cataclysm was supposed to change that, and it did to a point. We worried a lot less about dying from back-to-back melees. But spirit scaling failed to make healer mana a real constraint, so we ended up not caring much at all about total damage taken. Which meant that our deaths were generally due to spikes, rather than trickle-down “deaths by a thousand cuts.” It shifted our view from “need to survive two boss attacks in a row” to “need to survive 5-6 seconds with minimal healing,” but not to “need to reduce damage taken to preserve healer mana.” And the solution to a 5-6 second spike window is still EH.
We stacked mastery instead of stamina for a few reasons in Cataclysm, but the primary one was EH-related. Shaving 30% off of every attack is almost like having ~43% extra health (1/0.7=1.429). So we stacked a lot of mastery because it was, in effect, an EH stat – it made all of our stamina much, much more powerful, and made our damage intake smoother. In statistical terms, we reduced the variance in our damage intake with respect to our health pools.
The fact that mastery was very good for TDR didn’t hurt, but it wasn’t the reason we stacked it – otherwise we’d have continued with doge and parry once we reached block-cap. After reaching cap, what did most hard-mode tanks actually do? Stack more stamina! There are a variety of reasons why, including more spike survivability, better interaction with magic damage, and the fact that stamina is often a better mana-saving stat than TDR stats are anyway.
MoP has changed things, but not very much. Healer mana is certainly being stressed in these early raids, but not because of tank throughput. In fact, I’d argue that tank throughput has not seriously stressed healer mana in any encounter released after Icecrown Citadel. A healer who’s sole job is “heal the main tank” isn’t going to run out of mana unless they’re severely undergeared or not playing very well (i.e. not used to the damage patterns on the fight). Or, in the healers’ defense, they could be healing a very bad tank that isn’t using their mitigation tools effectively.
So we’re in pretty much the same state that we were in Cataclysm. We care about spike deaths that occur over 3-5 boss attacks, or 4-10 second windows. There are a few edge cases, of course. Heroic Feng on 25-man, for example, can hit you twice simultaneously for 200k each, or 400k burst damage in a tenth of a second. And he can do this every ~2 seconds, making 3-second windows very dangerous. But in general, we still care about spikes, not TDR. Hit and expertise reduce the frequency of spikes. Stamina reduces the magnitude of those spikes with respect to player health. Both are important, but point-for-point Stamina does a better job of combating spikes.
It’s value obviously varies based on your situation: when you’re undergeared, it’s very valuable; when you’re slightly over-geared, it becomes less valuable. People frequently talk about gearing strategies like “stack stam till you have ‘enough’ health for the boss,” but I think that they’re misleading themselves. ‘Enough’ is nebulous – should it be 2 attacks? 3 attacks? 4? 5? – and I think stamina retains its value fairly well even above ‘enough,’ both because of the added survivability and because of its under-appreciated benefits to healer mana.
Unfortunately, it’s very hard to quantify any of that without building a simulation that literally re-creates WoW. My damage-smoothing simulations don’t include stamina at all, because they don’t include health at all. They just calculate the distribution of damage output the boss produces over time so we can see how large the spikes get and how much each stat reduces the frequency of those spikes. If we want to include stamina in those situations, we run into some significant issues:
- How much health do we choose as a baseline? This basically depends on how over/under-geared we are for the encounter at hand, which varies from player to player and from week to week.
- What do we do if the boss kills us during a spike? Do we keep running as usual, or terminate the sim and track this information (i.e. +100 stamina reduced deaths by X, +100 haste reduced deaths by Y, etc.)?
- How do we model healing? In the steady-state, your healers are producing more HPS than the DPS the boss is subjecting you to, otherwise you’d die very quickly on every pull. But that healing isn’t constant – it comes in discrete chunks (heals/ticks) at a variety of intervals (HoTs, heals with varying cast lengths) and at different magnitudes (having an excess of HoTs on the pull vs. a healer forgetting to heal you vs. a healer dying).This is probably the biggest problem, because there’s no one solution. Every tank has a different healing team, manned by different players, who heal differently. No one model can properly encompass how an “average” raid team heals, and it’s dubious at best to even define an “average” in that sense.
There are more issues, but even on this short list we’ve hit one that’s been plaguing theorycrafting for years. I remember having discussions about how to model healing as far back as early WotLK, Mel’s blogged about it before, and even to this day it’s a question that hasn’t been settled. If you model a “perfect” healer, the tank almost never dies. So you want to model an “imperfect” healer, because tanks tend to die when someone makes a mistake (healer or tank). But how do you model “bad” play when that sort of play is inherently inconsistent and varies from player to player and encounter to encounter?
As such, we’re stuck with some “hand-waving” (meaning “not rigorous”) arguments for how to relate Stamina to other anti-spike stats. I certainly don’t feel confident enough to say that I can “prove” Stamina is more valuable than hit or expertise, at least not numerically. I can at best make some good logical arguments why I think it’s better, and support that with a limited amount of evidence from logs, experiences, discussions with healers, discussions with other tanks, and so on.
I think it’s fairly telling that most tanks in the top 100 have traditionally gemmed for all-out Stamina, because they’re going into the fights fairly under-geared and prefer EH over everything else. But even that data point is limited in scope – not all top-tier tanks are theorycrafters, and in general they trust their gut and go with what seems to work. In practice, I think that they could be almost as successful gemming Spirit, because their success hinges far more on their sheer skill than it does on what 5 gems they choose. These players are so damn good at this game that the minor differences between gemming stamina, avoidance, or control stats isn’t going to make or break their progression.
So in short, we really can’t come up with a clear numerical relationship between stamina and control stats like hit, expertise, and haste. At least, not without writing a simulation with AI advanced enough to impersonate 25 flawed raiders making mistakes in a non-uniform, slightly randomized, slightly deterministic manner. That’s the sort of task that’s well beyond the limit of “easily modeled.” You could spend years doing a Ph.D. thesis on artificial intelligence and WoW raiding and still not have a suitable model for that behavior. The best we can do is make some educated guesses about how much we should value the two stats based on what we know, what we can deduce logically, and what we can surmise from browsing logs.