Getting hit for 20K from steelbreaker is nothing new. Whole Ulduar is all about having different gear from previous content and balancing out what you need.
I'm pretty sure that all hard hitting mobs & bosses (except kologarn) have parry haste so it might be advisable to get more expertise.
With 30-40 expertise I'm getting hit for same amount as you but each 2 sec which gives more then enough time for my healers to react. Insta gibbed only once due lag failure (holy light overheal landed on me 0.01s before punch + melee + punch tick).
Mookey | GM of <RISE> Xavius [EU]