My guess is you're playing a pirated copy that doesn't have the performance patches...
...So because you can run the game just fine with your setup means that everyone else having a problem must be a pirate?...Piracy has nothing to do with it mate.
I'd have to agree that comment was less than helpful - particularly since "cracked" games (where the original used media-check DRM) typically ran faster (SafeCast and SecuROM disc checks had a 10-20% framerate hit).
...As for the OP, you can only wait for Larian or Nvidia to decide to do something about this. I've been posting constructive posts regarding this issue on these forums for over a week and all I have gotten as a response is that Larian is "aware of the issue"...
In fairness to Larian, performance issues
should be lower priority since most people have workarounds (lower graphics settings, lower resolution), whereas those with crashes, conflicts or game-breaking bugs do not.