I went the fred flintstone route to OCing - Asus has a "F-Stream" app for OCing automatically and i stopped at 4.3
a) you might try dropping the OC to 4.3 to see if you get similiar temps to mine - if you do, then it's the OCing
b) higher voltage will also add heat or raise temps, you might try dropping Vcore voltage 1/10th volt at a time and running Prime95 v26.6 - when you hit the voltage where it crashes, then bump voltage back up a couple of tenths, and see what that does to temps.
what i said earlier about a "big drop" of thermal paste, you can put too much - try a couple of small grains of rice size drops, clamp it down, then remove to see what kind of coverage you got - if you got decent coverage, clean the TIM off and re-apply...