First off, I'd quit. Boxing is the only reason I still play as I was pretty tired of the game.

Second, it would be extremely easy to get rid of boxing and they wouldn't have to change anything other than say it's not allowed. It's extremely obvious when someone is boxing by watching and probably even easier from Blizzards point of view where they can see the timing of input to multiple characters. All they would have to do is start handing out bans, problem solved.