I've had similar problems on my i7 @4.4, 16gb ram, Nvidia 680GTX, 2 x SSD's (OS on one, Diablo 3 on another).
I haven't managed to completely stop the issue but I have reduced it by doing the following: Enable V-sync and triple buffering, not from in-game but from the NVidia control panel. From within the games video settings I've also enabled the 'Max foreground FPS' and set it to 150 and the 'Max background FPS' also set to 150.
This made things a lot better, but it still stutters every now and then, the strange thing is that it seems to get better after a little bit of playing, it's like it needs to load stuff up into memory the first time or something, so after a few mins of playing it gets 'warmed up' and it runs better. Of course the best solution I found was to play torchlight 2 instead

but maybe that's just me.