Yagluth fight was alright to solo using Frostner and Drauger bow with silver arrows when melee wasn't an option. Good food, potions and moving around are key to defeating him.

I also prepped the fight so 1 of his attacks was easy to negate and another wasn't nearly as lethal. Plus no enemies could join the fight.

https://steamcommunity.com/sharedfiles/filedetails/?id=2903119953