This is a quick tip that makes it easier to think of tactics. If you press "v" in game, you'll see the red bars that belongs to your enemies(after start that is)
This works over a pretty long range and through LoS. Just drag your mouse over the red bars and look in the right corner and you'll see their classes and stuff.
You wont see stealthers or Hunters feigning death.
This makes maps like Blades edge mountain easy, just stand in your starting room for like 5 sec after start, find out their classes and rush. If you got some kind of voice communication, it'll be even easier to decide your tactics.
I've done every arena and it works on all of them, although at the Orgrimmar arena, it might be useless since you start right next to eachother.
Searched and found nothing, read through several PVP guides for this.