I did have FRAPS working with LA Noire when I played it. I don't know, maybe a patch to the game messed up the framerate counter software, I played before the patch that added DX11 support.
The problem is that like all recent RockStar titles is it is poorly optimized. The game's framerate is also capped at 30FPS. As such, the game does feel a bit laggy as in the driving and certain outdoor sequences the framerate can spike down to 27FPS.