Oh dear. Oh dear dear oh. If you were going for status land, you about got it, just that there's a bit too much of it. A bullet hell is at least maneuverable. There are so many poison clots and firey monsters setting these alight that it's more of an unavoidable wall of death. So much fire infact, that my computer had a bit of a break down towards the end. I overall think you were too liberal with the fire.
Enough making the entire thing look bad, I really liked the new enemies. Only real complaint is that their dash attack is almost instantaneous and so fast that it often results in them seemingly teleporting behind you: while that serves as a cool attack it instantly leaves you poisoned and possibly on fire from their trail. The boss however, was too easy. Knocking him up into an upper corner, he just stood there while i wailed on him. Though, after the rooms before, I'm not really complaining there.
So, I'd guess as a TL;DR, too much status clots, make the boss do something, and this would be a good challenge. As is, the walls of death make for extra cheap difficulty.