http://rog.clgaming.net/blogs/reign-of-elementz/2307-champion-pick-statistics-from-dh-how-correct-is-my-tier-list-afterall-for-high-level-play
I know Elementz is considered one of CLG's deadweights, but I do appreciate his site when he posts hard data. Not that this is an amazing reference, as it's based on his bias with which champions are "Tier 1".
TL;DR:
Most often banned champs (from Elementz' Tier Guide) throughout the tournament:
Rumble
Twisted Fate
Nidalee
Vladimir
Alistar/Vayne (tied)
Most often used champs on winning team:
Ashe
Nunu
Janna
Alistar/Corki/Jarvan (tied)
Unfortunately, it lacks data about the champions that Elementz doesn't consider "Tier 1". I would have liked to see ban data about EVERY champ throughout the tournament.
inb4: LOL ELEMENTZ WOULD BAN GRAGAS LOL