When you get Nsu to the light room be warned he likes to marry pillars. We were doing it on elite at level and after he was near dead from the light. He said screw this im going to hop into this pillar and marry it. sticking his tongue at us because we couldn't hurt him. not even flame turret or intimidate worked.
Had a ingame gm help us. Bug report was also submitted. So just a warning to all. Nsu loves Pillars.