The new trend with the more experienced players like me now is that when playing with Twelve, we use the Super Art X.C.O.P.Y.
If you are good enough and know how to use the other characters competently, then this Super Art can win you tournaments. The super doesn’t take that long to build up for if you are good and can be done at least once each round. That’s all you need to win.
With X.C.O.P.Y. you transform into the opponents character with extra high damage. If you don’t finish them off during the Super Art, just poke them to death with normal Twelve.