Good point - I didn't play WOW, but in EQ (I know..) I had a choice of a few different zones I could head to and grind some xp. I mean there were a bunch at certain levels.
Here you're pointed in one direction, the same direction, over and over. I guess the problem is that it all needs to be done through quests, and everything in the game has a voice over and cut scene.
They are actually limited on content by how fast they can do the voice overs and cut scenes...