I think the main thing is to name them separately.

Having them in a train is a complete giveaway (that's actually how I thought I was supposed to run in the beginning, heh). Additionally, I think not using huge mounts that attract so much attention is another thing. My guys are still just flying 200gp swift riders they got when I initially got epic flying.

I've landed on the horde zeppelin in Icecrown and there were several guys there all on their epic mounts that happened to match mine. They swarmed up around me and were encouraging all of my guys to huddle up for a screenshot. They honestly thought all my guys were controlled separately even though they flew up and landed together. Perhaps my server may just be full of idiots.

Ah, additional note:

Running a mixed team probably helps too.