The XP loss in 11 was one of the best things about the game. You really fought for your life, having your team wipe was a disastrous event for all involved. In games like WoW, death is little more than a minor inconvenience, and really only costs you what time you put into that mission. It sucks, but oh well, just try again. In 11, you really feel bad when you die, and you play the game much more carefully as a result.
I really liked how Guild Wars handled experience, though. You hit max level very quickly, along with being able to get max weapons and armor. From there it's all about your skillset and strategies for the diverse amount of missions and raids. The game was really well-balanced for it, and you didn't have to worry about being underleveled for quests for very long. Of course, such a system wouldn't work well in all games, but I really think that GW is the type of model people should be looking at (especially for PvP).