I watched the part of the show where Tatiana won her award on Hulu. I don't think the people in the room were too familiar with the show or the actor because her win got a rather subdued response. She had some stiff competition (Viola Davis is a superb actor), which makes her win even that much greater. It reminds me a bit of Bryan Cranston's first win for BB. I cannot imagine, nor have I seen a better performance by a female actor this past season, not that I've seen all of them.
IMO, the fact that Tatiana plays multiple parts is only a small pert of the magic she brings, the brilliance is the way she plays each character. You could take any one of her characters and drop them into another show and her portrayal of that character is still likely to stand out. Her fully realized and nuanced presentation of each of the character she plays stands on it's own. This is the way someone on an obscure BBC show beats out a Viola Davis.