I have a level 50 DK and she is great for self healing and gaining ultimate really fast. Her DPS is nothing to shake a fist at either. I tend to move around a lot with my characters to avoid being hit when possible which in general reduces the damage I take but also increases the time it takes to take an enemy down. In general with my DK I rarely have to heal. I also have a night blade who deals nice dps but I find she needs to heal more because I can't steal health from enemies and she also does not gain ultimate like my DK does. I can go a really long time before I have enough ultimate to use an attack where as with my DK I seem to be able to use an ultimate attack multiple times in a boss fight (and I am only doing delves and quests solo so short fights).