You are correct,
I have just got upto him again in my latest game (3 days and completed all bar sarevok and TotsC bitz

)
He uses dimension door after a while, so u have to kill him before he does this.
His AC must be massive, as even Coran and his bow skills cant hit him much. Magic and Magic and Magic are the way to go i think, as he doesnt have protection against it. Dispell his once he has cast his protections stuff at the start to give yourself a better chance.
Get someone with mirror image or likewise protection next to him so he targets them with the fireball...
Then he shoots a LOT of lightning out, which can be nasty :P
I have yet to beat him, but im off to have another go now
