I have this damned Problem with those Stutters since WOFF's release in 2013. My Suggestion is quite simple: It has something to do with the Graphic Settings in the Game.
I am playing with a GTX 970, 8 GB RAM and a i7-6700K with 4 GHZ. A pretty fast System, I think. Every Game on my System is running smooth as silk with High Settings, believe me. But I still have Problems with WOFF. Campaigns from April 1917 onwards are stuttering as Hell.
In OFF Phase 3 we've had more Options to tweak the Graphics. Do you remember the Graphics Config in Phase 3? You know, those Settings with the "Overrides" and "Texture Info" and so on. Tweaking with these Settings allowed the Players to adjust their Graphics, until OFF was running smooth and liquid. I am still playing OFF, and I have tweaked with those advanced Graphic Settings, and even with heavy Air Activity in 1918 I can play smooth as silk, better than it was ever before, I never see any Stutters, a very nice Gameplay.
But WOFF doesn't have these advanced Graphic Settings anymore. And THAT is the Problem IMHO. What runs good on the Dev's Systems, must NOT run good on our Computers, even if it is a similar System. I wish we had more Options to tweak the Graphics. But I have surrendered to it, surrendered to this whole Problem. THERE IS NO SOLUTION TO STOP STUTTERING.