I would say that your video card is beginning to meet its match when it comes to performance. NFS: Most Wanted is pretty graphics heavy, and it might be a little too much to run 1920x1080 at high graphics on your GPU.
You would have two options here, upgrade - to something like the HD 7950 or 7970, or drop the graphics settings. Within this option, you could split into two again - drop the resolution to say 1280x720 and keep the graphics up on high, or keep the resolution at 1920x1080 and drop the graphics settings to a mix of medium/high.
I would say it's normal, and as new drivers come out (as you've stated) there should be performance improvements, but they're usually limited to around 5-10% boosts.