That one is pretty tough I'll give you that. You have to make a beeline for the "puddle" on the floor and occupy the real estate as much as humanly possible. Spam projectiles. Use health related konsumables to punch your life back up if you get pushed out. Also consider using "Orb of the Dragon King". It gives you a Fatal Blow outright and you can get a second one when you drop to 30%. Also, blood related konsumables of your own are pretty good. "Severed Head", "Ball of Coagulated Blood" and "Plasma Infused Death Rocket" in particular.