Thought I'd post a quick update.
I had a 670 and was getting stuttering with FIFA during gameplay and also a very bad slo-mo effect when playing Batman AC in the steel mill, whilst walking past machinery giving off sparks, and also some general stutter. Another member reported the same issue with Batman, but I think moving to the 301.42 drivers solved it for him.
In the end I decided to RMA and go for a 7970 instead. FIFA now runs perfectly so appears to be a 670 (driver) issue but Batman AC still chokes at exactly the same points, so in my case at least would appear to have been a 'false positive'.
I am glad the 7970 sorted out your prob and I can see your point on a game you enjoy playing (fifa12). It would wind me up TBH and good honesty on the Batman AC. This could infact just be a coding problem more than a driver problem.