Friendly reminder that fire damage deals extra damage and can be used to break the ice armor removing the buff that it gives them.
Hope this info helps others like it helped me, because before I learned this these guys were more difficult than most if not all of the bosses.

Man do i hate these things, maybe i'm underleveled for the area or something, but i simply can't deal enough damage to kill them legitimately. every time i've killed one of these damned things it's because their AI is crap and it yeeted itself off a cliff

he's done with your bs