Be sure your camera is zoomed out so you can see most of the battlefield for this fight.  Block all blockable attacks.  When he burrows underground, run a few feet back immediatly and keep running in a circle around him as he will come back up and cast 4 red dots on the ground under your feet that will knock you in the air if your standing on it.  Once the 4th has been cast, run back to him and get ready to block another attack.  When you see a golden bush spawn, immediatly run to it and stand on top of it.  You will see a sheild around you.  He will cast an AoE attack that will take about 25% of your health if you are not on the golden bush.  Rush and attack once he casts the AoE.  Rinse and repeat.