GTX 1060 i5 6400
GTX 1060 i5 6400
I don't have the same configuration, but I might be able to assist based on the issue you're facing.
I understand, in Far Cry 3 my GPU usage stays under 60% all the time.
varies by game; some run smoothly at 60-70% because of CPU limits, which usually happens when you're playing demanding titles. In less demanding games it uses nearly all GPU power, though your 8GB RAM might limit performance. I recommend upgrading a bit more if needed.
It makes sense, given your CPU specs, you might need more RAM. As long as you're maintaining a solid frame rate, I wouldn't have major concerns.