Actually I'm advocating a rather regular distribution of the quests, instead of having very little to do for the first levels and everything focused in the mid-to-high ones.
It's not a horizontal curve. Ranks 1-25 =/= ranks 26-50. There doesn't have to be much to do for the first levels because they're not going to take long time to clear anyway.

And why exactly they shouldn't be?
Because like I said, not everything has to be designed for leveling up. It lengthens the experience in a good way too. The longer it takes to get to the cap, and the more stuff you can do during the process, the better. At the cap nothing helps you level up anyway. Why the rush to get there? It's why Rift is failing as we speak. "Journey was better than the destination", oh really? The developers ought to keep that in mind as they keep developing the game.