When I started Samarri to catch him up i needed to level to 12 before granting levels if I wanted to hit 60... in the noob area there were 4 other dual boxers starting out. I leveled to 12.9, granted to 60, and then spelled up and geared up off the AH (basics) and hit the trail on my shaman quests for totems...

By the time I was 61 with all 4 totems, a guy who was 5 when I was 5 was approaching 20... We chatted a bit, his goal was cat form before he called it quits and it appears that is where he stayed... http://www.wowarmory.com/character-s...hand&n=Buffbus

At least on Blackhand I haven't seen more than 2 other high level multiboxers and one is alliance.