Enrage timers are a worthless and lazy way to design content in any game. Either I can kill the mob with my group, or I can't. Why should it matter how long it takes me to accomplish my goal? Dead is dead.
I'm from EQ2 and that mechanic, while it does exist on some of the higher end content, is used as an obvious timer mechanic and doesn't just wipe you but starts ramping up the difficulty while leaving you a chance if you start executing well.
Enrage timers shouldn't exist in any fashion - they aren't fun, they aren't challenging and they bring nothing to the event. Pure Dev Lazy.
Plus they rob the player of those epic fights that last for a long time and you never know, do you beat him or not until the end.
For example, there is a jedi champion on aldereen that I could probably solo, but given that she enrages and kills me instantly i can't after all. Without that stupid enrage it would have been an epic battle. Right now its just crap.