So, after having finished the SR 1&2 Remastered earlier this week I felt the urge to play Defiance now. I installed it off of Gog, added the Widescreen Patch set to my resolution (2560x1440), enabled VSync and capped the framerate to 60fps. I also checked the process and it's supposed to only use a single CPU core.

However, the game becomes very choppy every few seconds. Does anyone have any idea on how to fix this?

I just too passed SR 1&2 Remastered and started (and finished) Defiance this week, but I did not had any troubles like that, though, I didnt't install the Widescreen Patch and my resolution was 1080p at 144 fps, I changed it In GOG Galaxy on options and ... edit I think. The game ran great though I was stuck in some part, but it was the game design fault not anything else.