Your CPU is fine.
Try either unlocking the 4th core, or try overclocking.
Tried unlocking the fourth core when I got it last year, no luck. I have it overclocked to 3.1 on stock voltage with stock heatsink. That's the best I could do. I could get it to 3.2 but the voltage increase and heat output was too significant for my taste. I may consider a better heatsink/cooling solution down the road for a higher overclock. I'm just going to wait until I notice a bottleneck in my games.
Thanks for all of the advice!