Maybe it isn't so much that warlocks are able to self-rez then it is that they do it. Think about it: Hunters are tasked to scour the land into enemy territory, constantly risking their lives for the hunt. How would you feel if you had to constantly stare death in the face and have to survive, while some schmucks can just throw their lives away, knowing they could easily come back moments later? From my perspective, this would seem to be like an insult to those who accept they won't make it back from such suicide missions, and would prefer to die with honor than to just have a crutch to help them.