The Jailer's Gauntlet: Layer 5

One of the things to watch for and play with at these higher levels is the timing of when mobs spawn. Some spawn when others die, or when they hit 50%. This means that you can periodically hit a point where if you're against a single mob or even a couple that aren't overly dangerous you can just let your CDs respawn. It also means that if you die when some mobs came in because you hit one to 50% you can destroy your run since you're now no longer in a position to kill the 6 or 7 you now have up at once. The first level tends to be the source of most of my deaths, later levels with additional powers get progressively easier.

ilvl 254 4 piece blood dk, seems to be nearly impossible to beat this level because elite mobs spawning 3 at a time all with knockbacks/fears or insane damage abilities