Also, please tell us how you would go about proving that anyone who leaves a WZ isn't doing it for real life reasons and to avoid xp. Unless you can video tape that 49 in person playing, showing that he didn't, in fact, have RL issues, you can't prove it.
You realize that they have data on pretty much everything that happens in game, they just have to put something in place to use it. So, if they are getting reports of a player leaving warzones just before the game ends (who would leave at this time, you get no rewards after playing an entire match), then they can look at the data to see if that is the case and take appropriate measures.
AFAIK they've never needed videotape to ban hackers, I don't see why this would be any different if players are found to be continuously leaving warzones to avoid XP.