I'd say it really shouldn't be doing that, I have an i5 3570k @ 4.4, gigabyte ga-z77-3dh, 8gb (2x4gb) kingston 1600, sapphire hd7850 2gb oc edition and haven't had any stuttering at all, I'm not very far into it yet but I've came across some action and had no problems.
I've also found that if I have it in fullscreen, instead of fullscreen windowed (what I play with), I have the same problem, but it is even more constant, so much so that I have around 30fps all the time! It's unplayable in fullscreen, and in windowed it's choppy. It's a real shame, as I want to play it so much, but I simply can't enjoy it like this.