Just have to learn how to fight them, they'll go down about as easy as any other extremis. Aim for the cannon on their back when they hunker down and learn their attack timing. I took one out with just the neo volkite by shooting straight down its barrel and popping the spore mines right on it.

They need to nerf the siege mode it needs to be headshotable even in siege and must be able to be forced out of siege by melee and getting kocked over by them running away is frustrating to no end

Literally made an account to make this post. The Devs need to know that any enemy that the solution is "just don't fight it, lets just leave" is not healthy for the game. 
Some enemies I will avoid fighting during specific moments. I have never felt like it was worth it to fight a biovore. No grenade type is effective against them, they can knock you over by walking away from you, and they can just be immune to damage. They easily feel like the worst thing in the game and I wish they would get reworked to just be a little less annoying. At least zoanthropes move towards you constantly so you don't have to spend a bunch of time running after them. 

I think they are okayish. A bit too tanky and I find it very frustrating to get hit by a mine after getting run over by them. I think the biggest problem is when there are 2-3 in Absolute and they just run around and flood everything with mines to the point they just explode to your face.

I find it very rude to just say that it is a skill issue. I got many runs on absolute with basically zero damage taken, so I consider myself being at least somewhat good at the game, but when 3 of those come up, the run almost every time is over. Even if insanly good teams that happened many times.