You can three hit each with the solar sword and doesn't cost a super. Killed all three many times before the ship even showed up. Takes 15 seconds if you're a Nightstalker though. Stand on outer side of solar flayer so each hit takes him towards other two. Use tether right as he dies with blood bound and you'll kill one in two hits and the other will die from perk. This is why the gunslinger is useless for bosses.