I am using the i7 4790k as the title suggests, with a z87 Killer board and hyper 212 evo cooler. The chip is not being overclocked at all, but Core Temp is reading at 74-77c when playing GTA V or Witcher 3.
What case are you using and how is the ventilation? How many intake and how many exhaust fans do you have? Where are they located and how big are they? Poor case ventilation can cause higher than expected temps. What z87 board do you have? Make and model? Are you running the voltages on Auto? Maybe the bios is assigning unnecessarily high vcore. "Auto" is not the same as "Optimum" necessarily.
It is also possible that your cooler mount and TIM spread needs redoing. There may be poor contact between the cooler base and the CPU face or the TIM coverage is incomplete.