In that case I killed him in under a minute using the Sun Fury just dragging it behind me and occasionally jumping to kill the heads for health - this caused the weapon to bounce up and down - effectively hitting the WoF several times within a few seconds.
I overestimated how difficult he would be and paved a road in hell from one side to the other(small world). When I finally fought him I didn't even end up using 1/3 of it. I only had to heal once and didn't even use the potions for buffs I made.
I died my first two attempts because I misjudged my jumps and landed in the lava. After the second death I just paved over the lava pools and destroyed any towers in my way. The road wasn't flat, but there were no spots where I could need to focus my attention on my jumps.
The best advice anyone can give is just to build a land-bridge over the lava pools to focus your attention on him.