I'm currently playing on a low population server/battlegroup (Ruin, EU) and I've yet to join an AV where the Horde start off with more than 20 players and the Alliance don't heavily outnumber us. And as for EotS, I only queued once, and that was for over an hour before I simply left.
I remember reading a while back that Blizz were gonna do something about this, like having cross-battlegroup BGs, but has anyone heard anything recently?