I understand if it's not high priority but it would be nice if you could find time to fix this.

Same here, and I had same problem in Arma 2 as well.

Specs:
i7 3770K OC@4.4GHz
GTX 670
16GB ram
1920x1200
Win7 x64

Currently using "High" preset for settings but it happens on various settings, both higher and lower than that.

More detailed info with settings and graphs in my post here:
http://forums.bistudio.com/showthread.php?147533-Low-CPU-utilization-amp-Low-FPS&p=2314119&viewfull=1#post2314119