I'm not going to go into the whole issue of that you're just essentially wasting your own time if you enter warzone and leave before it finishes, so you can perpetually stay lvl49. Others have done that already for me.
I will, however, call you out on one thing. You are abandoning your teammates for your own selfish reasons (to avoid getting experience) and bailing on your teammates is wrong.
How does it hurt his team if a 49 leaves at the end of a match? I haven't played my twink in a while, but I'm pretty sure you don't actually get the xp until the scoreboard pops up. There's a long enough delay when game ends and the board pops for anyone to easily leave WZ.