i like this thread. there are a lot of points made from many different perspectives, and a lot is to be learned.
that reply sums up just about everything there is to tanking. love it love it LOVE IT. allow me to put in my 2 cents if you will:
i've been using hypatia's guide as a reference since i've read it, and i believe his perspective and the math he applies is very useful in this argument.
i'm going to show how often CoK is up when you are 1 hit away from dying, and how often it saves you from dying when it is up. this depends on how hard the boss hits you, so that variable will be H.
first off, CoK activates at 35% health, which changes based on your hp pool: 0.35(HP)
next, we need to find out if the boss hits hard enough to put you in danger of being killed by the next attack without CoK being activated, as we will use a different equation for each situation (unless we used an 'if' statement, which i will not for simplicity's sake): H >? 0.35(HP), H <? 0.35(HP). let's assume H > 0.35(HP), since we're dealing with t6 bosses here
ok, we just need to know how often CoK will be up when we're 1 hit away from dead:
sweet, we now know how often CoK is up when we're REALLY in the danger zone. (unfortunately i'm on a different computer and can't pull out an excel spreadsheet, and i'm lazy so you can input different values for HP and H on your own and see how this turns out.) now what we need to know is when we're in the danger zone, how much does CoK help? well that depends on your avoidance! let's check this out: what is my total avoidance? (miss + dodge + parry) = a. ok, now we need to include the CoK dodge buff (just going with a static 8% for simplicity's sake), compare our avoidance w/ and w/o the buff, and see how often the avoidance buff saves us:
w/o CoK: death = (1-a)% chance on next boss attack
w/ CoK: death = [1-(a+0.08)]% = (0.92-a)% chance on the next boss attack
ok, let's find out how much more often equipping CoK will save you compared to how often not equipping CoK will save you:
that is to say, if given passive avoidance a and in a situation where H<0.35(HP), you will survive the next hit (1-a)/(0.92-a) more often with CoK than w/o CoK. put them together, and you get:
note that with high values of avoidance, the CoK dodge rating becomes substantially more effective, and with the CoK and popping Moroes' Lucky Pocket Watch, a properly geared tank can effectively shut off damage completely in such a situation.
now, to find out how often you're 1 hit away from dying, i refer you to http://www.tankspot.com/forums/tanks...y-results.html as hypatia describes burst time and how often to expect it very eloquently (you should be reading this thread regardless).
perfect, now we have some formulas to standardize the CoK buff. these formulas are rough and i assume the same HP and avoidance with or without CoK equipped (which can be changed easily by your own math), but they are nonetheless effective formulas to find out how good CoK really is for you. let me know if you see any flaws in my argument or necessary simplifications. again, it's all a balancing act and like anything worth its weight in gold, CoK can be a godsend in some situations and negligible in others.