You better be ready to summon your mabari at the first second of the fight. Sure, is not a heavy dealing damager as our sweet hound back in DAO but at least it will help you do a little damage over time. Then…
RUN FOR YOUR LIFE. Run around the pillars and wait for an opening.
I specialized on fire and ice attacks so if you are doing the same, be sure to cast Winter’s Grasp every time he makes his horrible, horrible Charge. That will hopefully slow him down enough to give you time to cast Firestorm AROUND A PILLAR.
Start running around the pillar again.
If the Winter Grasp is not ready when he starts going again for a Charge, try to cast Tempest, again around the pillar and keep your distance at ALL TIME.
He will get you eventually, so be ready with the Health Potions or Heal spells.
I should have re-spec my spells with Arcane Shield and Rock Armor but meh, I forgot completely about that. Certainly good spells to have in this battle and don’t worry about the mana, you’ll get it back while you run.
Do not stop to fight if you are not full HP and just run if you are hit.
I managed to do this on the second try but it was really, really hard and took me a while. About 5 or 10 minutes to finish the fight. If you have any other suggestion, please share it in the comments!