You wont find one "best" line up for every situation. Certain ninjas that are junk for 1v1 arena could be really game changing in Ranked, GNW, or SA. That said, one of the perks to MB is that it's fairly easy to give them a line up that, while not being great at everything, preforms solidly at most things - without needing a bunch of expensive or rare ninja. They help of course, but aren't absolutely required to do well.