I am afraid I have witnessed the same thing, again.
I made this video with my Core i5 2500k@4.3Ghz and 7950 (same as r9 280).
GTA V will eat your cpu for breakfast
In this video the cpu is shown to be running at very close to 100% and the framerate is less than 50fps for the most part.
I have benchmarked my GTX 970 with the same cpu (with higher settings) and in the outdoors section it was above 65fps, were the 970 kept the game at a gpu limited situation, as it should be, with cpu usage less than 85% although I used higher clock for that benchmark.
I will post the real life gameplay video, along with 570,5850 and 7950 custom gameplay benchmarks once they finish uploading, which will be a couple of days.
Also note that these recordings are recorded with an external recorder, so no cpu cycles are wasted with the recording itself.
Until then, I can post other videos that I have uploaded that may be of interest for some people. Warning for spicy wallpaper on the last one.
GTA V graphics settings and impact on performance
GTA V this is what could happen if you go over your vram limits
Grand Theft Auto V 1920X1080 v.high (fxaa) GTX 970 @1.5Ghz CORE i7-860 @4Ghz
I have to say though that I was surprised that the game run as it did, on the 570 and 5850. It seems to run on a leaps and bounds better code, than the one on GTA IV.
I will also make a Q9550+GTX 970 GTA V video, for people with weaker cpus, so stay tuned.