sadly leveling as a boxing team is extremely slow, im 5boxing and im doing it through quests only doing the instance one time to get the quests done ... collecting quests take forever as A: droprate sucks:B you need more then the usual 10 for 1 character so it takes forever
you could just solo instances (well youcan't with 2 though but you could ask a friend to boost you through ... allot ) as instances go faster (elite mobs and everything) but it's so boring that I prefer questing