That's a terribly false conclusion you've made there based simply on an overall 50% usage of your CPU with your hardware.
i just disabled multi threading. Got 5 fps boost and GPU usage now hovering on 98% instead of 90%, and CPU usage hovering on 80% instead of 50%.
EDIT:
btw what other conclusions could be concluded from underused CPU and GPU with multi threading enabled, but disabling multi threading results in perf boost and higher CPU + GPU usage?