I beleive a blue poster stated that they are suppose to be just like the Tamers when battleing and are currently bugged on the PTR (currently at work so can't find the link). So you phase when fighting (no worries about getting ganked), they do not despawn when winning/losing/forfieting, and multiple people can fight them at one time. Now I am not on the PTR so I could be wrong, if so I'm sure someone will correct me.
"Even when you are winning soundly, you must always give your opponent a way to retreat with honor. If you don't, then he has no reason to surrender. He will fight until the bitter end, and you will pay a larger price for victory."