This was really difficult for me. After many playthroughs I found that staying small was the only way for me to survive. Evade and regen with some shooting. I regretted any offensive picks, even though they were the funner options. I just couldn't survive. So the boss took a long time, but I could stay in one spot and shoot. The regen handled the hits.
Had lots of fun. I think the offense vs defense needs some balancing.