Well there is one idea that may or may not work, it seems like it could work on paper but it would require a little TLC to make sure its not rigged or cheated. Instead of making just a PvE experience turn ins, you could alternatively accept daily quests for battlegrounds (or repeat after via reset stone) that requires you to participate in an X ammounts of games or win an X amount of games. (My thinking would be half the number of wins, which would give the incentive to participate, if you lose you aren't punished you just have to play another game or two.)
But most of you are probably thinking, well what about level and gear balance? Well the answer to the level range would be just to make different level requirements, say one room you can be 135-150, another room 115-134, another one 99-114 and then 99 and under. Gear on the other hand, I'm not sure the game engine could make it so certain gear wasnt allowed. It would be marvelous to have some sort of gear ban (i.e. god items, mvp cards, certain mini-boss cards etc.) just so it would make it more fair for the general player.
And then lastly, how to fix people throwing games or using alts? Is it possible to accept only one IP at a time? I'm sure maybe someone would have another answer for this, but then maybe it wouldnt be such a big deal if it was level requirements are set, but i'm sure it would get bypassed somehow.
Recap for people who tl;dr
make battlegrounds give experience via turn ins.
edit: Fixed after popular demand.
Edited by Fonzie, 22 November 2011 - 06:07 PM.