Hey,
1) You should run a BENCHMARK to see if you score similarly to identical or nearly identical systems. Something like Unigine Valley to start though you have to compare the EXACT settings.
I found the new "Time Spy" benchmark if you have the appropriate 3DMark benchmark was pretty accurate when it finished and I compared to a similar i7-3770K + GTX680 setup.
2) I suspect you do NOT have a problem.
3) Another way to test is monitor GPU usage and frequency for benchmarks like Unigine Valley. You should see your GPU hitting close to 100% during that with the frequency being what you would expect (1300MHz or whatever).
*If you see close to 100% load at an appropriate frequency for the GPU then your graphics is not fundamentally...