You know, there's a way that developers can test game-changing updates before releasing them for everyone.
It's called a beta.
TF2 does it (albeit only with gamemodes and maps, not with balance changes). Dota 2 does it. League of Legends does it. I swear, CS:GO is the only game with an established competitive scene I've played that does not have a beta testing branch that players can sign up for and test guns like the R8.
If this happened, we wouldn't have guns that were broken and ruined competitive play. Making new weapons OP is one thing. I remember the CZ, and I still think that the nerf it got was harsh, but the R8 is a disgrace. I think that a revolver can have a high risk/reward meta. I think it's neat to have a gun that isn't full auto or semi-auto, i.e. a mouse click doesn't immediately fire it. I don't think that that gun should be relentlessly OP from day one.
No matter how you spin it, a gun in a competitive FPS that can kill players in one shot with such accuracy should never have made it off the cutting room floor without rigorous testing by pros and beta testers. It should never have happened.