This is probably off topic to the current discussion.
I've been reading a lot of tanking guides for Death Knights lately and every single one of them has some sort of statement that looks like "The number 1 priority for a tank is to hit the defense cap of 540".
Does anyone else think that this statement is very disputable?
Consider this scenario: A Death Knight with 515 Defense, 50% avoidance with Blade Barrier up, and 28,000 buffed HP is tanking 10 Man Naxxramas. The trash mobs in the instance range from lvl 80-81. The Death Knight is 25 Defense away from cap, which means he has a 1% chance of being critically hit by a boss, and 0.4-0.6% chance of being critically hit by trash. There is a 1 in 2 chance that a mob attack will land. This means that for every 500 attacks the Death Knight takes, a lvl 80 mob will be able to land a critical strike once, and a lvl 81 mob will be able to land a critical strike 1.5 times. (I hope I didn't screw up the simplest math ever, I was never very good at it -_-''). As for a boss (Let's assume he's MT'ing Patchwerk since everybody loves using this boss as a benchmark, and because our Death Knight is very poorly geared we will spare him the fate of Hateful Tanking), for every 200 attacks the DK takes, he will be critically hit once. Now this is a rough guesstimate, let's assume Patchwerk attacks twice in one second, and let's also assume that the raid's DPS blows and it takes a full 6 minutes to kill the boss. For every 100 seconds, Patchwerk attacks 200 times, resulting in one critical hit. Over 360 seconds, Patchwerk attacks 720 times. This means that over a course of 6 minutes, the tank will be critically hit 3-4 times. Patchwerk hits for roughly 4500 on plate, so let's assume the worst and the critical strike landed for 12,000 dmg. The Death Knight has 28,000 health.
With the way that our tanking gears are itemized, Naxx epics puts more emphasis on avoidance/stamina over defense rating, and heroic blues puts more emphasis on defense rating over avoidance (Hell, a lot of blue tanking gear has no avoidance on it, but it does have a load of defense rating). Following the rule number 1 of Tanking101, replacing blues with Naxx epics seems idiotic and foolish since it would take them well below the defense cap. But what is the real value behind reaching 540 defense in the first place? I understand the need to eliminate the element of luck from raid tanking, but in the case of death knights, doing so would mean sacrificing so much raw avoidance and stamina. I've ran into so many new DK tanks who refused to replace their current gear with what clearly is a huge upgrade in terms of stamina and avoidance because it was a huge downgrade for defense rating, all because the number 1 rule of tanking "Hit 540 defense first, then focus on other stats".
I guess with the release of Rune of Stoneskin Gargoyle, the issue is a moot point by now. Still, I was one of those naive DKs who refused to replace my blue shoulders with T7 because of the downgrade in defense. Is it really a wise idea to state that the most important thing to a tank is defense cap when clearly (at least from my point of view) is not?
I'm sorry if this was brought up before, but I really don't have time to skim through 102 pages of tanking discussion

.