Just checked the timeline and you are correct, for some reason I thought the Acolyte was set in his time and not 100 years before phantom but..I googled if Raven would appear in the Acolyte and its a strong rumour that he will cast by Kanu Reeves like you just pointed out its the wrong timeline but he was one of the most powerful Sith/Jedi's who could heal himself maybe he worked out eternal life, bit of a stretch your theory sounds bang on the money and more plausible
I didn't notice the Sith in with the witches, will have to re watch that episode and pay more attention ha.
Yes, was something about how they was born in a different way mentioned, think your bang on the money again. When did the rule of 2 come in though? seems like we could have alot of Sith running around at the moment