Don't forget that they have to "overdeliver" on XP because diplomatic/stealthy playstyles kill much,much less enemies and therefore get less xp. Killing everything in the first few areas and finishing some easy sidequests puts you at level4 pretty fast in EA atm.
I have no problems with reaching higher levels fast and then having no progression later because I "powergamed" the start of the adventure. I think they have to tune the progression curve to players that won't murder everyone.