I think its fine as it is, sure it takes a while but thats the point. Would be a bit stupid if you get a level each dungeon. Then you will hit level cap super quick and then complain that there is nothing to do. I just got my 2nd level 60 this weekend. Which seems decent enough.

Some guy I know already has 8 level 60s... although he is a college kid who dont have work and is pretty much playing 24/7 during summer break.