I do believe that you need to take a look at the Boss Traven Blackdagger. Running redq today brought up Cragmire Crypts Epic. Dungeon was completed, but the issue is with the last boss, Traven.
[Combat (Self)] Critical Hit! Traven Blackdagger deals 314009 (624623) Fire Damage to you with Fire Bomb.
No Red area before the attack hits, it deals massive damage even after mitigation and the worst part of it is that this is a 13k min il instance. I dont know of any 13k il players that have 300khp (maybe some tanks out there..maybe) but the fact that there is no warning for the attack, no way to dodge it and doesn't just target tanks makes this attack in desperate need of review and fixing.