With less the 50% mitigation (or better, with less then a certain amount of armor below which you get an "invisible penality" to the amount of damage you get) you will not be able to tank anything, even in Kithai HMs (except Necropolis and Malice).
Better spend points you put in Dread Shadow in armor from General tree, or you will be able to just offtank, and just more or less by popping Dread.