I had no trouble with him on my templar, or really any character, but that is because I build for self-healing at the same time as damage.
I use heavy armor with a magicka focus and anythign that heals while I do damage. Then you just stay out of red, block when you see white lines radiating from him and bash to interrupt when you see red lines radiating from him, or any enemy.
I didn't actually have trouble with any enemy in Nchuleftingth except the duo Renduril the Hammer and Friar Hadelar because they unfairly have an AoE that pulses stunning you every second to 2 seconds with no CC immunity triggering.
That boss duo is just broken unfair compared to every other public dungeon boss.
My Templar is stamina and there was a pile of adds that are dwemer guardians and they all pound on me and even with my healing I'm dead in no time. I can't kill him fast emough
I know this is old, but I got it on Google, myself. Hopefully, this could help someone else out.
After a couple of tries, I thought for sure it must be impossible and I'm just missing something - there are 6? giant golems, and while I was trying to kite them, he had a long-distance lightning zap that did something like 4k damage a pop.
Third try - apparently, it is possible. For my sorc, who is pretty tanky, it took a LOT of kiting, dropping lightning flood while I kept up daedric shields and ran dark channeling to keep my magic topped up. It took awhile, and I had to carefully control my kiting to keep AoEing the main guy without ever giving more than one golem a chance to stun me at any time. It was the least fun battle I've had in the game so far (I hate kiting - especially the panicked kind!).