I recently leveled 3 toons to 90 by mostly chain queuing dungeons and questing a bit when the queues were too long to wait for. I had no heirlooms because the server was new, and i didn't feel like i needed to gain items by other means than dungeon drops and quest rewards. *shrug*
You may be overreacting with this or at least over-thinking it. The leveling process these days is so quick and effortless that you level so fast, quickly leaving behind anything that you may buy from the AH anyway. There's literally no reason to buy something off the AH, only to replace it in 4 levels which go by so freaking fast in 2013 WoW, and for what? You are going to do 100 more spelldamage or such? Back in vanilla you may have had a point because even the first 10 levels took over 6 hours of gameplay time, and after that, each level was increasingly longer until where you would have people who would stay at the 50-55 level range for weeks to 1 month.
Are there fewer options to gear up your character? Yeah, one less, big deal. But it's made up for by the bag of goodies you get after each instance which will cover the neck, bracers, rings, capes, glove and even belt slots. Not to mention, the questing rewards are lightyears better than anything the pre-revamp vanilla leveling zones could even come close to.