Anyone who claims this game is much more casual than SSBM/SSBB clearly enjoyed the Meta Knight/Meta Knight vs. Meta Knight/Meta Knight team tournament finals at APEX.
Balance has nothing to do with how casual a game is.
Street Fighter 2 basically gave birth to competitive fighting games, if not fighting games in general and that game featured Akuma, a character so broken he's universally banned in tournaments everywhere.
Also this year, I believe they've limited it to 1 MK per team. Doubles should be a lot more interesting this time around.
http://allstararena.com Competitve Hub for Playstation All-Stars Battle Royale