Yes, i did not think that an OC-ed 8700K at 5ghz would bottleneck a RTX 2080Ti.
So it is indeed strange if you are getting FPS drops as bad as you are.
I am running on an Aorus RTX 2080 Extreme and i can hit 270+ fps (altohugh i cap it based on my monitor’s, Acer Predator X34P, max fps) on High to Max settings but at a lower Render Scale .
I did not try out Low Settings on 100% Render Scale because Render Scale affects framerate more than settings do. Of course, that does not answer your question on why the RTX 2080 Ti is outperformed at the same Render Scale and Settings compared to the GTX 1080.
My only guess is unoptimised drivers.
Aorus Engine had an update a day ago and NVidia also just released a new driver 1-2 days back. You tried both?
btw, on “Scan” and “Active” fan mode, the Aorus Engine managed an auto overclock of up to 1950mhz for my RTX 2080 extreme. Just something to share. That the latest version of the Aorus Engine looks to improved.