@Game could you imagine something for spec mode? ( i don't know if it would be hard or even possible to do it) : autorize to spec only char of your own account.
As you can log multiple chars of the same account, it could be something interesting, people will have to participate the killing to get xp while their other chars would benefit the xp of the account owner.
There's a lot of people who go on inferno cows when there's an announcement but don't do anything, in fact, they go in the game to leech xp, and then, continue to play on another player/game.
This could be a solution to make players more active on xp games