It certainly is a waste of time in this case, unless there's a specific reason for it. If the CPU is already far beyond what the game needs, it's just overkill and you will not notice any improvement in quality or playability; the only way you would see a difference is if you are looking at benchmark results. You'd be doing it just to do it. Is that worth $100? Not in my book.
Overclocking can certainly help a middle-of-the-pack CPU give you a better experience, but for a top-tier processor that kills games already? Forget it.