Sporadically when engaging an NPC I notice that my mouse becomes very sluggish. Checking my FPS it settles at around 20. Strange thing is that it's always 20 and it never seems to happen consistently. The frame rate drop extends to navigating store listings which still run at 20fps.

Anyone else notice this? I'd blame DOF but my framerate is consistently in the 40-50s at max settings (without uberampling) with far more taxing calculations going on.

It is one of the depth of field effects that does this. Try disabling one or both (I can't remember which one it is), it will fix it.

Yup I did this and my dialogues and cutscenes went back to normal.