Some advice on getting black spindle that I have not seen mentioned really anywhere. The adds come in waves so do not even focus on shooting the boss instead push into the room and clear all adds and take down the blights. Once all adds are cleared DPS the boss. At a certain health level more adds spawn, stop DPS'ing the boss and clear adds and blights again. Once adds are gone go back to DPS'ing the boss. The last wave of adds (I believe 3rd or 4th maybe can't remember, but its the last wave) spawn yellow bar shielded captains. Swords should be used to kill them down fast at their spawn point (side entrance in the room) exotic swords here are nice. Once that wave is down finish off the boss. Reminded me very much of the Skolas fight in PoE minus the mines thankfully.
My group kept failing on this until someone joined our team that showed us this strategy and we beat it with like 30 seconds to go on our first attempt.