The majority of these games happen when I'm sleeping so I haven't been following the tournament much, I do talk about it with someone a bit though. The other day we were talking about Io, and seeing how OG's ana has been dominating with it.
Back in my days of playing Dota I remember Io being a mostly support hero, and seeing how OG's ana is playing Io and even getting an ultra kill and a godlike killing spree is just crazy. So for me Io has been the best hero in the tournament so far.