at some point, frame increases stops helping. overclocking can improve frames, but once the frame increase is redundant, then it is pointless to OC.
the 4790k will run dayz mod, may times, over 100 fps on my system. in instances where it doesnt, and is 70, 80, 90 fps, there is no significant help, or noticable difference that i get from the frame differences at these times.
now, going from my old system where it would struggle to get 20 70% of the time, when i would get 30 frames or higher, there is significant difference and noticiable help that an OC would give.
if you get the 4790k, you can overclock if you want. keep in mind that it may not produce any additional benefit to you (depends on what frames you are getting to begin with before the OC and what the OC produces in extra frames).