I've run AMD System Monitor next to ARMA3, but i never got above 60% usage of my CPU or GPU. Other games take about 80/90% of both. My game is stuck at 25fps at low action, and drops to a whoppin 10fps if something tend to happen on screen. Turned everything to low at one point, but doesn't seem to help much.
System:
Phenom II X4 965 BE
Radeon 7870
8g ddr3 memory
win7 64 professional