I think I have a cause for the Dark Face Bug:
https://www.creationkit.com/index.php?title=Dark_Face_Bug
This would explain why some don't see it. I tried this and it worked, but then I got the red forehead bug. If I remember correctly, DCL had a similar problem a few updates back.
I solved that by turning off all the tints and then exporting the face gen data.
I use Fair Skin, btw. I'm not sure if that has anything to do with it.
https://www.nexusmods.com/skyrim/mods/51602
Take a look, tell me what you think. Some be