You have to make a good team each time to beat your opponent, every time you have to improvise.
I got an earth main (yes, cuz its the only playable role with free ninjas against the p2p players), I was fighting an lighting main (survival) and at the first round he was doing 4 hits and combo to my kabuto(4th place) letting him live with half hp... Imagine if in the 2nd round you have a combo as well he will die and the team will be useless.
As they told you before, dont expect to win everyone with the same main/team.. you have to change each time.