Hunters counter any Mages as far as I know.
Ele should kill them especially if there is obstacle involved. Warlocks generally should kill hunters, Destro more likely than Affly, dont know about Demo. Boomkins only if obstacle is involved.
Shadow no questions.
Well yeah it is more like 50/50.
I agree that ranged classes will be more viable in pure PvE gear while in BGs vs coordinated teams. In arena, Prot war/pala, rogue, feral should be better.
It is fun to do BGs with Prots, but if those ele/warlock guys just target you and melt in seconds, because you are in front lines, it will be hard to enjoy those forever retreating games.