This happens every event. Too many people chose the popular team, the minority team wins because there are too many people fighting to kill the minority. The minority can do whatever it pleases.
PROPOSED SOLUTION
Gaia, are you listening? Very simple fix [to someone who has no programming knowledge]: Make the battle system events a flash game. How is this done? We had a Halloween event years ago where we would fight NPC monsters and ghosts in a flash space. It was incredibly fun and entertaining, much like the Christmas event where we rescued the orphans. You succeed based on your performance. Even if you have a team, it is easier to balance out performance because you do not have the issues we have been experiencing with the battle systems. What say you?