Unfortunately yes, there is only one set of zones per faction for each level bracket. At first (who am I kidding, it still does) it struck me as kind of odd, but I guess it's understandable considering how the game is designed.
With Thieves' Guild I believe, you can choose whichever alliance to quest in after you reach level 50 (cadwells silver and gold), this is a step in the right direction but it doesn't really fix the issue with leveling alts.
I wish I could go anywhere once I reach, say level 10, and choose what zones to quest in and what quests to do. I wouldn't mind it if they enabled a mode where you could just skip all zone main quests and only focus on side quests and still get skill points, but maybe that's just me. It's not really an issue, but it sure keeps me from making any new characters.