I've beat him four times: once as a rogue, once as a mage, twice as a two-handed warrior.
It's a hit and run tactic. Hit him, run, hit him, run, summon dog to distract him, hit him, accidentally get impaled, drink potion, run, run, run, fail to stun him, get knocked over, get up, get impaled, run until my potions are useable again, run, hit him, run, use stamina, run, hit him run, hit him, run, Hit him, run, hit him, run, summon dog to distract him, hit him, accidentally get impaled, drink potion, run, run, run, fail to stun him, get knocked over, get up, get impaled, run until my potions are useable again, run, hit him, run, use stamina, run, hit him run, hit him, run, Hit him, run, hit him, run, summon dog to distract him, hit him, accidentally get impaled, drink potion, run, run, run, fail to stun him, get knocked over, get up, get impaled, run until my potions are useable again, run, hit him, run, use stamina, run, hit him run, hit him, run, hit him, run out of stamina potions, have one health potion left, barely kill him before dying.
A liberal sprinkling of swearing in many languages at the tv. And that's the battle.