Well if the maximum possible burst damage of the Boss was 1 Damage more than I could take then I might even prefer 1 HP.

But you are right, that in the majority of cases the 10% dodge would serve me better as it has a higher chance of keeping one alive (for example when my healers are asleep/disabled) than 1 HP. Thus you can't completely take out avoidance of the survival game, but for a more indepth answer you could just scroll up:

What you really don't understand is that the game has changed.

You no longer die from one hit, as you used to, most boss (azgalor, archimonde, supremus, shahraz, council and Illdan ) can't crush, and having a large HP pool to mitigate those hits and being able to live through that one hit is no longer an issue, Kael being a notable exception, due to his pyro.

We aren't discussing how to gear up to tank Prince Malchezaar in full blues here.

What can kill you, and will kill you if you go for HP only, is repeated high damage hits, especially with 'parry haste'.

When you tank Illidan or Archimonde and you take a serie of high damage streak, you can die off it. Illidan dual wields can hit you for a series of high hits at a 1sec speed, and cream you down pretty fast.

The only way to prevent such death is by avoiding a few of those hits, and that's where avoidance comes to play.

Now i think we'll all agree it really depends on the fights. For Kael you need HP, for Illidan, you also need avoidance!

To sum up, just use the little avatar to the left of the posts, and compare which you would trust to know high end tanking between the Tank with illidan gear and the mage with crafted spellfire or the karazhan raider.

Either way it's not like we are discussing the difference between going for 60% dodge with 5k hp versus 30k hp and 5% dodge. The choices are rather tiny, such as gloves enchant, trinkets some gem choices etc, and in the end you only have so many options available to you at a certain level of raiding.

I think you are defending points that even the best tanks (which aren't uniform, either. Some focus more on stamina/mitigation than others) you are "defending" wouldn't make.
First what you mean to say is probably that the *some* encounters have changed. Most underlying mechanics haven't changed in this regard. And I'm not sure where you get the idea that you used to die in one hit at some point (actually sharaz might be closer to this state than any tweaked raidboss before) in the game and this isn't even getting close to the full argument for focusing on stamina, which I won't rehash for you yet another time.

Even the BT/Hyjal tanks you are referring to are heavily focusing on stamina, as being bursted down can still be a big deal, even though they are already outgearing BT.

But you are up to something when you say that bosses are hitting faster for less (and are additionally not being able to crush) their damage also becomes less streaky, making avoidance *somewhat* a little better (the faster the boss hits and the lower the amount he hits for the better avoidance becomes, by a small margin, though, as it averages out faster, yielding less danger, than slow, hard hits). I wouldn't go out and say this is the new standard, yet, though and Illidan still hits pretty hard.
I even seriously doubt you absolutely *need* large amounts of avoidance on Illidan, but I won't doubt it helps. But so would stacking more stamina and mitigation. You still need to understand the underlying mechanics to make the right decision.

At this point you leave me no choice but to wonder wether *you* actually have any meaningful tanking experience as I seriously doubt the good tanks you are referring to are "sometimes" (when they get lucky with their avoidance) surviving on encounters like azgalor, archimonde, supremus, shahraz, council and Illdan, but they actually survive most of the time, bearing something else going wrong than their avoidance streaks. Remember you get hit a lot during a 15 minute boss fight and the chance for your avoidance to fail on you increases over time and you are almost *guaranteed* bad streaks even with high avoidance.
Only once you are at a point where you will receive a statistically minor amount of bad streaks on a given bossfight (like 0-2) you might be able to reliably live through those bad streaks through your emergency buttons (shieldwall, last stand, consumeables, trinkets etc... maybe some awesome healer will throw a big NS heal at you, but I think this can't reasonably be expected), but chances are you will blow your cooldowns too early or at the wrong time, as you can't predict wether the next hit will kill you or not (since avoidance is random) or there is another mechanic you might need these cooldowns for than a bad avoidance streak.

The choices being somewhat limited does not alleviate the want for some people to be able to make rational choices. Nobody forces you to jump on that bandwagon, but apparently even dots would like to know a rational breaking point between stamina/mitigation and avoidance. And actually, as you *closely* approach 100% „Full Avoidance“ from dodge and parry, the survivability gains from additional avoidance become similar to the gains from additional stamina/armor and eventually surpasses them (infinetly even, when it comes to physical damage).

Over at tankspot someone did the math for effectiv health theory and has build a calculator.

TankSpot - Effective Health

That said this is more for fast progression or under equipt tanks than for the guys with every tanking item in the game or access to those. Sure when you are able to get all T5 thats and can decide between 2 or 3 gloves. The TE and myself are still not near Keal at all we do the progression through SSC and TK. When you don't have access to T6 and MH/BT Items this is no option to go for. Most of the guys in discussion tend to go from their current status and don't remember the choice that they had back when they were in SSC. without even the access to T5 shoulders from VR.

From what I see as RL and Feral Druid with healing experience it is much better to stack HP and Armor instead going for avoidance for the time till Keal is down.

From my limited expierience of healing in BC, I must say the the worst thing is not controlable damage spikes. The healers start to get a rhythym for the attacks of every boss and land their heals just when needed to maximize mana reg strategies out off OOFSR.

I think you need to put the focus more on the *closely* part than you have done so far, though. 50% avoidance is not nearly close enough to give avoidance more survivability gains than Stamina in the majority of cases.

I really suck at math but I think this is called exponential function.
I'd estimate the sweet spot in pure survivability gains where avoidance surpasses stamina in giving more survivability per itemisation point beyond 90% for the majority of encounters ingame and that is why you see tanks stacking stamina, not avoidance when choosing gems.
At the 100% mark you can survive with 1 HP as long as the damage is solely physical (meaning your effective value of HP goes to 0). At the 99% mark, however, you will still need enough HP to at least take one hit, preferably even 2, so the relative value of Stamina is infinitely higher.

Choosing the perfect tanking gear might not quite be "rocket science" but its a lot more complicated than say calculating relative threat values (thats why we have addons being able to simplify the latter to a point where the whole system seems dumb, whereas we don't have anything like this for the former, yet). The Calculations and rules on tankspot are very far from being complete.

As a healer, a mitigation-oriented tank is definitely easier to heal.

Consider a setting in which you are healing either an avoidance tank or a pure stamina/armor tank. We will assume that both tanks have enough max hp in order to not be insta-gibbed, so that the only thing we need to consider is the hp buffer.

On the mitigation tank, having a larger hp buffer, as well as taking less damage per hit, allows each healer to plan their heals much more consistently - it is very possible to determine the incoming DPS on the tank, since the variability of incoming damage is lower, and spikes in damage don't need to be reacted to as "harshly" since the tank still possess enough of an hp buffer to perhaps not need an instantaneous boost of healing to keep them from dieing on the next hit.

On the avoidance tank, the better paradigm of healing (generalizing, of course) would be to heal cancel a higher rank. While over the long run, heal canceling a higher rank may result in less mana usage, it results in less PREDICTABLE mana usage. A healer cannot plan their cooldowns as well while healing an avoidance tank, since they do not know when they have to heal, whereas with a mitigation tank, mana usage has a lot less variability (even if it is not perfectly constant), such that a healer has a much better idea of how much mana they will spend in the next 30-45 seconds, and can plan their cooldown usage appropriately.

Here's some real world experience with parry flurry so other people know what we're talking about. This is what we like to call really, really bad luck with a boss who can crush.

I have 20k AC and 20.6k HP fully raid buffed, and I didn't have a chance. Given my gem, enchant, and other gear choices, I think it's pretty hard to argue that I'm not a stam/AC focused tank. He parried 3 of my attacks and instagibbed me. With an ironshield pot on one of our first "let's see what this fight is all about" attempts I might have shaved under 1k damage off of those hits. It still would be enough to kill me unless I'm 100% topped off, which is never going to happen against 4 attacks in 5 seconds. I'm in mostly T5 gear and by no means undergeared for what the fight intends. Could I have survived that if I were a Tauren? Possibly.

If these types of attacks come up frequently once you start getting further into zone, you have to stack some avoidance.

Tanking is part art, part science. Intuition should tell you "hey, I can't survive the hit, so I have to rely on luck". There are way too many variables to plug that into a spreadsheet and say "ok, here I have the penultimate tanking suit for this/every fight!" It just isn't going to happen.

You have to know your healers and know the fight. Every guild is different and every tank should use common sense to figure out what the smart choices are based on their strengths as a guild and as a player. There might be certain gear load-outs that you commonly use for a first-time encounter or for trash, but in general you'll tailor your gear for each fight once you start getting past T5 content. It really is that simple. By that point you really should have multiple armor pieces that are each focused on different stats. You wear different gear for different fights and stack according to what's required. Any amount of time spent parsing the combat log after the fight should tell you what you need to wear the next time you engage the encounter.

Figured that I'd drop in my 2 cents for what it's worth, and Fellwraith pretty much nailed it here, and I'd say that's true even in the T5 content, and even maybe before that, though clearly there are fewer options when you have access to less gear.

If you can die to a couple of hits, and it's clearly possible that more stam will let you survive more of these bursts (Gruul with the growths and silence effect seems to characterize this perfectly), any options in gear selection should be used to gain more stam and armor. Same but focusing on stam and ignoring armor if most or all of the damage in the spikes that would kill you are magical damage, or unavoidable for some other reason. If you can't get enough stam to survive another hit, then clearly it doesn't help much.

If it tends to take 6+ hits to kill you, avoidance can start to be really useful. The shaman in the Karathress fight or tanking Morogrim come to mind, both have a ton of individual attacks in the 3k range or so that can add up to kill you quickly. Going from 50% avoidance to 51% decreases the chance that a given 6 attacks all hit from (.5)^6 = 0.015625 = 1.56% to (.49)^6 = 0.013841... = 1.38%, about an 11.4% reduction in the chance this will happen. This can add up fast, and gets better the more hits it usually takes to kill you and the more avoidance you already have. Since even on these fights it usually takes disruption to your healing during a burst, and you have pretty good odds usually of surviving with last stand or trinkets even then, the drastic effect this can have on how often you have "oh shit" options up when a burst does happen can be really nice, and if it takes 6+ hits to kill you you should have time to use one. Naturally, avoidance is also better than stam when you have no hope of stam increasing the number of hits it takes to kill you as well.

On the other hand, at least what I've seen of the game so far, if you have enough healing to throw at a problem, almost anything can be solved by enough stam and armor. Whether this is how you want to handle everything is more or less up to the raid, and if you can kill a boss with either method which on is "better" is more or less pointless. Personally, I think stacking a bunch of healers on the main tank can put them to sleep and cause the tank to die to a huge spike just as easily as high avoidance gear can, but this largely depends on what the healers are comfortable with. Either way though, you want a full stam set, you probably want some more avoidance oriented gear to swap to in the slots where you have a good option (aka, not the blue quest avoidance ring with no stam on it, avoidance isn't THAT good), you want a set of block value gear possibly mixed with some +hit gear to maximize aggro on trash and bosses that won't kill you and you want to fly through quickly, etc. If you have the gear to make one, you may want a passively-crush immunity set that would be an alternative to straight avoidance gear on bosses that hit really often if you have problems with shield block dropping and dying to crushes. With the upcoming expertise change, wearing max expertise will make sense when parries can kill you, or for threat generation.

Overall, yes, if you had to rank items for a "general purpose" raid tanking gear set, there'd be different ways to value different stats. On the whole, like many have stated, there aren't THAT many options gear wise though, and the "correct" answer as to which ones you want as a MT tends to be "all of them and I'll pick based on the fight." About the hardest place to make decisions here is with gems on items with red and/or yellow sockets and a good socket bonus (usually stam), and when in doubt you probably want to go with more stam, especially if it's clearly the overall best item you have for that slot. If you have multiple pieces for one slot and it makes sense to do so, you might want to gem them to match what the items are best in to begin with.

Since I do use lootzor.com to get a general feel for how the items stack up to one another, I do have numerical values I put on each stat for "general purpose" tanking, and usually for stam and avoidance stats I count 20 armor = 1 stam = 1 dodge rating (a fairly healthy lean towards stam given it's lower cost in TBC), and rank the other avoidance stats based on how much avoidance they give compared to dodge rating, with some value placed on aggro stats at times based on what I'm looking for. This is fairly arbitrary on my part though, with just some rough math and gut feelings behind it, and rarely if ever drives my selection of what to use on a particular boss fight. To me though, ignoring either stam or avoidance seems like a "good" way to make content harder than it has to be.

I'd say that that WWS is pretty much a healing issue and not a tank gear issue. I do admit that you could use a better ring/trinket for this fight since the block value is useless here, but other than that, it seems that you do not have ancestral fortitude active. In fact you seem to be healed solely by two hotting druids and a paladin spamming Flash of Light. This obviously won't do. It just looks like people were reactively healing and well, were just being awful.

@Fellwraith: The problem for me with the linked WWS was tha fact that you were only getting constant heals from 1 Pally using FoL and 2 Druids HoTs, with random Chain/Waves from shammies. You simply cant tank "Worst case Scenario" with only 1 main healer and some HoTs. With a Priest healing you (Inspiration is godly for a mitigation tank) along with hots and the Palladin you would've probably survived that encounter and had SB up for the next hit

If your gearing for stamina then the healing needs to be consistant also.

This is Teron Gorefiend guys, a boss who can easily take multiple healers out of the mix due to the mechanics of the fight itself. This fight and Archimonde (who thankfully doesn't hit very hard) can be very good in keeping your healers out of the fight.