Let's discuss tactics/strategies on this mode.
Do you prefer to play with (given the chance) two attackers or an attacker and a defender? What I mean by an attacker is a partner that deals high damage; an defender is one who has high life, or has tricks up their sleeve in battle (essentially only Boo).
While I haven't played this mode in a while, my strategy would be to have a balanced defnder/attacker bringing up the rear, and an attacker up front. I think that when I played, I usually encountered my foe from behind (or vice versa), so this strategy would be fairly useful.