Very cool fight! Honestly some slight invincibility would be nice. Several times I took way more damage than needed. I understand if a bit more if I'm standing in poison. Sometimes it can be difficult to locate the boss but some more indication as to the boss switching attacks like a clear sound effect would likely help the player readjust their aim.
I do like how the boss can be taken down in under a minute, and has varying attacks. Taking it down quickly makes me feel skilled. Didn't ever feel stale or scripted.