Krosis is listed at level 50. I wouldn't reccomend facing him. Unless you really, really want his mask. Go for it.
If I fought the dragon and survived for 20 minutes Im sure I can kill him eventually.
I also got the Dark elf from the college being a distraction, good thing she is a protected NPC.
update: Im a nord, and Krosis seems to have run of out magicka and is using Ice magic, should I rush in?