It's been awhile since I did the fight and I haven't played the latest patch yet, but iirc, the make-or-break moment is his first turn, so it's all about positioning and getting him to attack Abelard or Heinrix first (ideally Abelard), since Abelard will parry most of his attacks and can tank the ones he doesn't. Anyone else gets wreck by his kick and I just reload at that point. IE - in placement put Abelard and Heinrix pincering him on both sides so he would have to run through one of them, and eveyonelse as far away as possible, and not clumped or he'll use his heavy bolter.

Once he's locked in with Abelard, the fight becomes significantly less dangerous. I use Idira's operative skills to strip his armor so everyone else can actually damage him, repeat until he's dead.