Hey there. The boss in the graveyard quest from the mausoleum isn't working right. He's supposed to be a really nasty caster who uses painful spells but instead he dispels you and then just spams acid splash. Underwhelming and it turns his room into a "kill the zombies and ignore the boss" type of deal.
I think he scales. Sometimes he casts a very nasty AoE spell and wipes out people not paying attention.
Not a bug. The AI decides what spell to use. Although could certainly remove acid splash as an option.