Sounds like a personal issue to me. I have lvl 90 toons on Illidan, Mal'Ganis, and Kil'Jaeden (All different battlegroups, IIRC) and I win 75%-80% as Horde. The reason people think their faction loses BG's is because losses are frustrating and overshadow your wins.
Edit: Seriously. Take a pen and paper and make two columns. One for wins, one for losses. Do BG's for an entire day or evening and tally and record each win and loss. At the end of the day, I'm pretty sure it'll be pretty even. (Make sure you blacklist AV/IOC though lol)
This post was edited by Nile on Jun 19 2013 01:15pm