Vanguard Monks

http://vg.curse.com/database/items/details/1209058/
So i examined the item tonight "Flawless Pariah's Jagged Tunic of the Marked" which has 177 crit chance on a few alts

Vs lvl 47 = 5.88%
Vs lvl 49 = 5.13%
Vs lvl 50 = 4.78%

From a simple equation, comparing the vs 50 and the vs 47, you can get a constant number to be used for extrapolation
4.78 / 5.88 = 0.8129                 (you also get this if you compare vs50 to vs49 and cube it - proof the equation is linear)

So if we put this number back in we can work out what the % crit is vs a lvl 53:
4.78 * 0.8129 = 3.89
Therefore the 177 crit chance is :-

Vs lvl 53 = 3.89%

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So...assuming the crit chance of most abilities can never exceed 40%
for APW (level 53s):-
40 / 0.8129 = 49.21%

You need a total of 49% crit (vs lvl 50) to be capped for Raiding

that sounds about right, pretty spot on with what tanks were saying as far as mitigation goes.

Yea likewise tanks would need:
65 / 0.8129 = 79.96% mit to be capped for Raiding