1 - Upgrade your armor to level 4, all pieces.
2- Poison resistance mead is a must here.
3 - I recommend iron shield and mace, upgraded to their highest level (blocking is a must in this fight.
4 - The sledge is good to switch to for the adds, just go to where he throws them and use your max level sledge and you will decimate the adds. Then go back to boss.
5 - I can post a video if these tips aren't enough. There are several on youtube.