Necrotic Plague : cannot target the tank. You need it to clear the ghouls/vrykuls from phase 1, however. The trick is to put an engineer dummy to drop aggro for a split second, LK gives you the plague, outheal it, then proceed. Use either AMS/Chains of Ice or Potion of Purification to remove it/prevent it from affecting you again.
Valks : Buggy as hell. Can't target the tank, they just mess around. They finally stop eating popcorn and grab me at some point... you'll have to watch to see when.
Defile : I stand in some of these on purpose in order to increase Vengeance. It has to be done very carefully, since both p2 and p3 are very healing intensive phases (p2 because of Infest which means I can't dip too low on health, p3 because of vile spirit explosions)
Frostmourne: Yet another mechanic that doesn't target the tank. Wouldn't be difficult to overcome in any way whatsoever, but would make beating the enrage impossible, so I guess that's a good thing it's not there.
Everything else can be found on the Youtube description (music, etc.)