One solution would be to download msi afterburner and watch the gpu usage graph. It should be near 100% utilization if there is no bottleck. You can also open up task manager to see how much your cpu is being used.
Cpu at 100% while gpu at 60% then you have a major bottleneck. Just mentioned MSI since i've tested with that one while i OC'd my GPU, using EVGA precision atm