It's hard to say.
If you stepped back in time and put them against the Fnatic Shushei team that ran Gragas/Ashe to devastating effect or even further back to a time where Hotshotgg and Elementz were duo-laners on CLG then it's possible they'd get their butts kicked.
A lot of teams were very good on their patch, in their era, and in their meta. Some things that have changed are natural additions to the game while others are reactions to new patches, items, champions, etc. All we can reasonably say right now is that C9 is strong right now, in this patch, in this meta.