I also have a 2500K, and I easily pushed it to 4.5GHz with an aftermarket air cooler without doing any voltage tweaks. So you can perhaps look at pushing it to 4.5 as well, depends on your cooler.
I don't have Overwatch, so I can't have a look to compare. If your friend's i7 sits so low, it probably means that Overwatch utilizes multiple cores quite well.
What are your Overwatch settings like? I see the high CPU usage seems to be kind of common if you google the issue. One suggestion was to push all your graphics settings to max/ultra, so perhaps try that.
Also, try other games to see what happens. Don't immediately assume it is the CPU bottlenecking your GPU. Overwatch might just be CPU intensive, or the game might just not be optimized that well yet since it is fairly new.
Here is a list of things you can try, nr. 12 is the one I suggested above.
http://eu.battle.net/forums/en/overw...1861242#post-5





