For what it is worth, after reinstalling the game today, the issues of Hotfix #20 seem to be fixed for me. (Intel iMac 5500 XT)
I reinstalled last night and they definitely were NOT for me. Also, it's hotfix #21 that seems to be causing the massive slowdown in graphics performance, not #20.
You may not notice as much unless you're running at a high resolution (eg., 4k) at max quality (Ultra). Who knows. There absolutely has been a problem introduced though as many of us are having the exact same issue since hf21.
