Last year we had this problem also. Today i installed GPU Tweak 1.6.2.6, and when stress-testing the gpu-clock monitor stays on 658 which supposed to give me 1974mhz or when in idle 1569mhz(performance mode).
It never goes higher than 658mhz in GPU Tweak Monitor.
But if you use GPU-Z, FPS-Monitor, or some ingame monitor its working good.
Can a Asus Rog representative here take contact again with Asus DEV and let them fix this once agian? (and why doesnt this get checked when they release a new GPU Tweak?)