If you're, say.. level 37. And you want another level 35-40 zone than the one you got right now, then you go there and guess what? You have to start with all the easy starting quests before you can finally at some point get the quests which are for level 37, not 34/35.
By that point your probably level 59 or so. (Warning, exaggerations might have happened.)
Since the rehaul of the quest lines you can't just start a zone at midrange. You just won't have any quests. In most cases you HAVE to do all the quests in one giant chain, no way to just skip the beginning and start with the interesting stuff right ahead.
It's another thing that highly annoyed me about cata leveling. :/