6600K does bottleneck the GTX 1070, Im 100% sure that it does, I am so sure of this as in bf1 me and my friend on the exact same spec setup both saw the i5 6600k overclocked @4.2ghz reach 100% usage. The 1070 was working at around 50-70%. I had to turn settings down 2 medium to keep fps above 60. I am suprised more people havent spoken about this. I experience simular issues in watch dogs 2 or any cpu intensive games. but ofc some games that are less cpu intensive use the gpu to almost 100%