Can someone explain this? There has to be some kind of fix, right?

I'm running an i5-4670K with a GTX 770 and am only getting ~35 frames per second, sometimes dropping sub-25, which is simply unacceptable. Booted up Witcher 2 to make sure nothing was horribly wrong, but nope, solid 60 there. Proteus clearly should not be this stupid-demanding.

Help? Surely there must be a solution.

Wish I can help you here. I have a 680 and an OC 2500k and get 30fps. At least its a steady 30 though. Are you having issues with frame lag or a frame rate that bounces around so often the game feels choppy? If you do, I would go to the Nvidia control panel and turn on the adaptive v-sync (half refresh rate) option. It locks the game at 30fps, and this lock prevents the frame rate from jumping around. This locked frame rate makes games appear smoother than 60fps game that dips to 45fps every other second or so.

Thanks, I'll try that adaptive V-Sync, because yes, my main issue is the choppiness. I tried limiting the framerate via EVGA's Precision X software, which usually works, but didn't seem to have any effect on Proteus--maybe because it uses OpenGL?

I've turned on my GPU usage monitoring, and the game's only ever using 3-4% of my GPU at most. Ridiculous.

Update:

Well, it's better with the "Adaptive (half refresh rate)" setting enabled. I can at least stand to play it this way, thankfully. But wow, how disappointing.

Thanks, @monetarydread!