LITTLE SPOILERS AND TIPS
Two tips. First is that you can lead him to the down, right corner of the dungeon where there pillar acts a shrine with no cooldown, makes the fight ridiculously easy as long as you have a companion.
The second one is to lure him off to the start of the dungeon as when you have killed him you can just exit and don't have to deal directly with his support. That way you get the quest but can return for the XP if his support is too strong. Remember to pick the items he drop, might be useful.
Oh and in the tomb there's a chest that holds a few items as well as a secret door way on the left side of the dungeon, between the left corner, down pillar and the upper, left corner pillar where's there's also a chest.