I've owned a similar spec'd laptop with GTX765M before and 45FPS on the open world is pretty much about right.

IDK, this game is honestly isn't a graphically intensive game but open world FPS seems to run a little low even with very good hardwares

I game at 1440p with a GTX 980Ti and even so, I only get above 60FPS 95%ish of the time. It drops to 45-55 range when in things like hunts.