I just searched in Youtube that GPU and Witcher 3 and performance was barely 30fps on low graphics. According to userbenchmark.com, my cpu is about 75% better, but my GPU is 500%I'm bloody serious. I don't know why it runs so well either.
Witcher 3 seems to be an extremly well optimized game anyways.
The few options I disabled barely changed the look of the game and I got pretty stable 30fps