The only thing deciding games is...
Which permabans slip through ban phase, and which team picks them. Enemy gets Viktor top, Irelia mid? You lose. Enemy gets Kaisa bot, Jax top/jungle? You lose. Enemy gets Camille jungle, Akali mid? You lose. etc etc etc
Champ balance is the biggest current issue. And we really need more bans if Riot isn't going to find a new balance team.