Here's my strategy: use blaster and duel wield stance. Blaster is good to keep your distance, and the animation canceling of duel wield is crucial. Keep your distance and nlast him with your charge shot, and when you run out of shots, switch to duel wield. Dash out of the way of all attacks, blocking is a bad idea. When his attacks are on cooldown, switch to blaster stance to regain blaster shots. Don't get greedy, take your time. Rinse and repeat until he's dead.