First post here and sorry if it sounds negative. I really enjoy the game but I'm also concerned about the lag, or mainly low frame rates in my case.
I'm running a Windows 10, i7 6700K CPU, 32GB RAM, GTX1080Ti GPU and I have only played in single mode so far but still experience very low frame rates.
I'm running the game in 2560x1440 at Ultra settings, but can't see much difference when lowering the settings.
Not sure this is so constructive but hope it helps you get this issue on the radar