Meeo gave me a nice tip for Phase 2 Black Knight that has let me 1-shot him every day since then:


Kill the adds.

I get a couple hits on the black knight to keep aggro, then just focus-fire down the adds one at a time. I'll taunt them off my team back to the center of the room, so if they do explode only my tank gets hit. I've also noticed if you drop your totems and move away from them, the pestilence gets cast on the totems pretty often so there's less team movement. I used to just try and burn the boss, but even though I could do it, it was a tough fight and I'd often lose a dps or two.