cacophonycat is right! I tried this guy 10 times before I realized some things: 1) keep moving ... ALWAYS! Run in circles around him. 2) Keep the Guardian Droid locked as your target. Don't divert your attention to attacking the adds. Once your AoE or best damage attack is out of cooldown keep hitting the boss. This will keep him off of your comp. 3) Stay out of his blast zones 4) Skip the kolto stations. By the time you stop to heal up your dead. 5) Keep your buffs up, especially any damage reductions. It's a massive slog but I got him in under 10 minutes.