The more I get stuck healing lately, the more I'm looking at our warrior tank's stats, and I'm seeing a weird phenomenon here.

I'm going to direct you to the armory profile or our warrior who tanked on our first prince kill: Braincracker

His combined Dodge, Block, and Parry total 63.51%. From what I understand, Boss level mobs have a 4.4% chance to miss a level 70 tank, and from his 506 Defense, he'll up that to 10.64. Overall, his avoidance rate is 73.51% with 28.04% of that being block.

Now we look at a typical raid level mob's hit table on him when he does not have Shield Block up (i.e. Prince phase 2, hit really fast!!)

Miss: 10.64
Dodge: 16.73
Parry: 18.74
Block: 28.04
Crushing: 15.00
Hit: 10.85

Now when his Shield Block is down, 15% of the time he's going to get crushed, while only 11% of the time he'll take a regular hit. In effect, because he's gotten his DPB that high, the majority of the time when he does not avoid a hit it in some way it will crush. As a result, his overall damage taken is incredibly spiky and is victim to the die rolls.

Now when you think about the tanks that take Stamina over Avoidance in any way they can and just barely reaching the Uncrittable cap for defense, they're at a somewhat lower amount of avoidance. Thus, while they have the same chance of being crushes, the damage coming in is at a much more predictable rate.

So is there a hidden area in the hit table where too much avoidance causes you to take an insane amount of burst damage that is difficult to heal through?

Well from a tanking side I've never had the opportunity to block an attack, and from a healing side I'm rather new (Just barely got my druid to 60 before TBC, levelled him up to 70 due to lack of tanks). While predictive healing is nice and all, but hard to always do (We had a frikkin prayer of mending stick on our MT for about 15 seconds on Attumen tonight).

Also, remember that if you're at risk of crushes, then the mob has to hit you 3 times within a 5 second period, which means an attack speed of 1.66, which is a 2.0 speed before Imp TC. I'm not sure how much Brain blocks for, at least 200, so considering that Prince is a dual-wielding mob, that's a fair bit of damage taken off a large amount of smaller hits and adds up noticeably.

You are going to get better answers from the tanks around here so I'll duck out before the waters get too cloudy. It occurs to me that the Thrash of the Prince is possibly the source of your perceived additional spikiness though.

Yeah, he instagibbed our tank Monday night with some REALLY bad crushes right after a Shadow Nova and I've been running it on paper since.

I'm pretty sure the Prince has the default 24% miss rate in phase 2. He's dual wielding there and misses like crazy. So the table would entirely consist of avoidance (parry+dodge+miss+block) and crushing blows.

Just a nitpick, shouldn't touch the core of your question.

As for the question: Yes, you'd get crushed most of the time when a swin connects in such situations as a tank. But you would NOT get crushed more over time than when you would have had less avoidance. I suppose thats the difficult part for the healer. You are getting deceived by a "lull" only to get a rough awakening when the hits connect.

drop the block down a little and up the dodge some more you only need a 25% block.

I don't see how your solutions help with the lull that is "dodge, dodge, parry, dodge, block" followed by the omgwtfjusthappened "CRUSH CRUSH hit CRUSH". If you took the time to look at our tank's armory profile, you'll see he has his imp shield block. However, there are mobs that just attack too fast to guarantee it to constantly be up. Dual-wielding mobs are the best example of that. Anything with an attack speed higher than 1.4 base can get a third hit in before shield block is back up.

Oh hey, he can do better than that. Here's it is without the deleted bits. It's a randomish sample too, I'm sure he's done much worse. After all, the bear lived.

20:24:32.125 Prince Malchezaar hits XXX for 4500. (crushing)
20:24:32.343 Prince Malchezaar hits XXX for 1974.
20:24:33.375 Prince Malchezaar misses XXX.
20:24:34.031 Prince Malchezaar misses XXX.
20:24:34.046 Prince Malchezaar attacks. XXX dodges.
20:24:34.046 Prince Malchezaar attacks. XXX dodges.
20:24:35.171 Prince Malchezaar hits XXX for 1641.
20:24:35.375 Prince Malchezaar hits XXX for 4753. (crushing)
20:24:36.375 Prince Malchezaar misses XXX.
20:24:36.609 Prince Malchezaar hits XXX for 5744. (crushing)
20:24:37.703 Prince Malchezaar hits XXX for 2327. (crushing)

He didn't Parry anything in there or do anything odd either, it's just his streaky thrash and high attack speed stuff. Be heartened though, the mobs get much worse than him soon enough!

Only 11 attacks in a 5 second period? I mean... glad I heal on that fight!

You of course use a druid tank, so he can't Parry. As far as "Streaky", I'm getting information from both sides that Malchezaar has a higher miss rate when he's dual-wielding. If he does, it's not as much as a normal DW penalty, 'cause that puts crushes at less than 10 when we have our tank raid buffed, and he has taken normal hits.

I'm really interested in what happened at 20:24:34.046 though...

Two dodges at the exact same time. I'm wondering if that's a case of coincidence or the dodge mechanic acting like a frontal physical immunity when you dodge, and thus evading all other attacks at the exact same instant. Heh, demo roar 50,000 critters up before taking on a world boss and dodge every attack because you're dodging at least one critter.

Those 2 dodges were the Thrash attacks that Prince gets in P2. Basically each of his attacks gives him a chance to proc Thrash which gives him an additional 2 attacks. Last night I tanked the Prince without any major consumeables but 30sta food and Elixir of Mastery. I did however have Imp, motw, fort and commanding shout. Very odd though that I was lacking 5k health off our first kills=/ really am totally puzzled bout that, but anyways... He can do some REALLY nasty burst damage in P2. We have 3 healers spamming me for the life of them and it got scary at times. Highlight of the fight was the raid leader (one of the healers) saying at 40% he is low on mana and its 20 seconds on his potion cooldown, so can I drink potions, and use my dodge trinket (I am a bear tank without a dodge trinket =) and use my healthstone to keep myself up till he can heal again. Sigh =)

All other things being equal (that is, equal hp and ac) more avoidance is always better. The odds of "Crush Crush Hit Crush" on a tank with less avoidance is higher than on a tank with more avoidance (because with higher avoidance the hit is less likely.) Certainly avoidance doesn't reduce worst-case burst damage, but it also doesn't make it any worse. More avoidance means less sustained damage over time. Even more important, more avoidance means less charges of shield block burned per second (and thus on average longer periods of crushing-immunity.)

The thing is your theory of "more avoidance = more crushes" is simply false. A higher percentage of the hits that land might crush, but of the total number of swings, the same number will crush. If your tank isn't using shield block, 15% of the time swings will crush, then 15% of the time swings will crush, and a tank with 0% avoidance is just as vulnerable to that (the odds of the crush streak are the same.) However if both tanks are using shield block, the 0% avoidance tank (let's assume the 0% avoidance tank still has 25% block chance) will be at much greater risk of the crushing streak. Why is that? Well the first two hits in a 5 second period will use up his shield block *every* time. Only 12.25% of the time will the tank not avoid at least one of the first two attacks, Meaning 87.75% of the time the 65% avoidance tank has his shield block charges last longer, meaning the period of time where your huge streak of burst damage in the fight can occur is reduced (and therefore the fight is much safer.)

So as a former healer, I feel I should point out that your complaint largely strikes me as a symptom of reactive healers. You should not be waiting for your tank to take damage to start healing. You should have a heal in the pipeline being cast pretty much 100% of the time even when your tank is at full health. If your tank hasn't taken damage, cancel that heal. If your tank is hurting, let the heal finish. A tank with more avoidance will not need more healing per second in burst situations than a tank with less avoidance (assuming equal HP and AC.) Ever since they changed the 5 second rule back in the molten core days, any time you aren't casting a heal you are probably making a mistake (because if you can reduce the average delay between your tank taking dmg and your heal landing by starting a heal before your tank takes damage, you ought to do it.)