Question Low GPU usage whilst gaming

Apr 10, 2019
Whilst playing games my GPU usage is really low and rather quite annoying as I am not getting the performance which I payed for. My specs are as follows:
CPU: Intel Xeon E3 1240 v3 (i7 4770 equivalent)
GPU: Zotac GTX 1080 AMP Extreme
Mobo: Gigabyte GA-Z97-D3H
RAM: 16GB DDR3 1600Mhz
PSU: 600W 80+ Bronze
SSD: 120GB
HDD: 2x 1TB 7200rpm
I play the games at a reasonably high resolution (3440x1440), with max settings, and yet my PC underperforms and the GPU usually stays around 60-75% usage (CPU no more than 60% on all cores). However, i have noticed that when I was playing the Witcher 3, the GPU would jump up to 98% usage and perform perfectly fine. This is especially frustrating as I bought a 100hz monitor but I can't even use it properly as games like GTA V are staying around 70 fps and then Arma 3 can be dipping down into the 20fps margin! The temps are also not a problem as, the CPU stays at around 50C and my graphics card stays around 70C. I have spent hours looking at other forums, and trying out what they say, but nothing seems to be working, I appreciate all the help I can get.