As you can see, Hardline isn't particularly CPU demanding as the Core i3-4130 wasn't a great deal slower than the FX-9590 or Core i7 processors when armed with the GTX Titan X.
Overclocking won't help Intel users gain much in the way of extra performance as an 80% increase in clock speed produced just 7% more performance.
It is difficult/nearly impossible to measure the true CPU requirements of Hardline as this needs to be done in a server full of players and for obvious reasons we can't reproduce accurate results in this situation. Therefore, our CPU results were gathered on a low populated server in the same way that our GPU results were.
Provided that enough GPU power is in play, those with an AMD CPU stand to gain some performance through overclocking. That said, an 80% increase in frequency from 2.5GHz to 4.5GHz resulted in just 29% more frames per second.