The reason for this is that BF4 is well known for being very CPU intensive. It's your CPU that is holding back your performance even though you have an i7. If you have MSI after burner you can see if your GPU is getting near 100% usage or not. My guess is that it will only be around 80% therefore confirming what I have said. If you had the game running at 1440p you would still get the same FPS. Try turning your resolution scale up to 125% in the game settings. If your FPS stays the same then the CPU is limiting performance.
Alienware 17 R4 2017 review