We need to know what version of Grievous this is. Even then, TCW Grievous has shrugged off being inside a starship as it exploded, having a propane tank explode on him, as well as several shots from the laser cannons of a republic gunship. Gambit would need to unleash his absolute best in order to stop Grievous, and I'm not seeing that happen before the distance is closed.
I was just wondering, you know how in the other thread we agreed Goro destroying diamond makes him at least as strong as Grievous? Well, I had a look on youtube, and from what I can see the "Test your might" challenges can be done by any character at the player's choice. If that's true, I wouldn't count them as canon or even author intent. Outside of that I'm not sure Goro's strength feats are too far off two venom'd up Banes.
Even if this is canon Grievous, we're talking about a guy who literally shrugged off being inside a starship as the explosives rigged to it went off. If he can take that, he can take a card or two on the way in.
Chewie rips the arms off of beings who themselves are strong enough to rip arms off of beings. There are levels to this arm ripping game, and wookiees are at the top of the food chain. Flash gets destroyed, mismatch.