Yeah you need the divine weapon to full kill his adds then he is gravy. Kind of annoying when his aoe kills the last couple hp of a skelly though and it pops up.
Also you did not see Solaire down there by the maggots? Hmm, I wonder if you missed a place you have to summon him. Not a big deal you just get his armors and it's nothing special. Except if you care about completing NPC stories for fun.