I have exactly the same issue. On laptop with Intel core i7, GeForce GTX 860M and 8GB of RAM, with fresh installation of Windows 8.1, and Divinity graphics configured by GeForce experience app I am experiencing the same issues as you are.
In my case I have copied my profiles folders from other machine, and expected this to be the culprit. Now I am experimenting with using newly-created profile, and copying only Savegames folders, will report on the results.
Curious thing - I have just entered "second" map - Silvergren and so far (one hour of gameplay) the stuterring problem didn't appear.
From my observation the pauses/stuterring happens mostly when game tries to load a sound sample for battle-related events.