Could be a CPU bottleneck, 10 fps sounds extremely low though, I definitely didn't come across fps that low in Deus EX.
If you run something like BF3 with V Sync disabled you should see 100% load or extremely close if everything is working as it should.
Normally low GPU load is due to a cap on fps in the game (either through V Sync or config files). Or through a CPU bottleneck not allowing the GPU to stretch it's legs.
The 10 FPS was in the Elemental Tower Defence map in SC2, not Deus Ex HR. Deus Ex HR never goes below 20, and that is with Tridef 3D turned on. With Tridef off I still sometimes get around 30 though, even with AA turned off. I didn't think it was the CPU at first cause it rarely goes above 30%, but then I remembered that since I'm on a quad core that I need to look at the seperated graphs for each core, and sure enough when I'm getting FPS drop I'm usually maxed out on one core. Probably need a better CPU, although I'm having trouble finding a better one that matched the LGA1156 Socket that CPU-Z is telling me I have.