I see a lot of issues dealing with stuttering but most of it seems to apply to certain areas of the game or frame rates with a lot of enemies on the screen. My problem is that my game stutters every second even when I am just sitting in the character select screen. You can hear it in the audio the sound of the wind keeps re-setting. Same thing happens waiting in town the town music just skips and restarts every second and the frame rate also skips visually. It is a recent development with Diablo 3 for me.
It also seems to be intermittent but does happen with more frequency some days while others it plays perfectly smooth with no changes made from me.