The problem is, I like to be challenge throughout the game, if I do every quest and the heroics once on each planet I end up being 2 levels above the next planets range (thru levels 10-32). If I do PvP or space combat its even worse. This makes all mobs very easy to kill and therefore no effort/satisfaction/accomplishment comes of it. I'm also an assasin so I stealth by a lot of mobs and their xp in dungeons.
So I have to limit myself and miss content so I can stay within a planets level range. I'm sure this is not what the developers had in mind. As I'm now 32 I'm "hoping" things slow down (ppl have said it does), in that case just the lower level quest xp needs to be adjusted.
Theoretically you should be able to do every quest on a planet and be just a little bit off the max level for that planets range or damn well near it.