Well said. Nyriss was a leading member of the Sith Council and therefore an expert on Vitiate's life and times. We can justifiably conclude that her account of events is not merely likely, but utterly accurate. She clearly emphatically states that Vitiate is capable of mindfvcking hundreds of Sith; no one has ever shown that kind of power. Vitiate would make pawns out of Sidious and Luke, and Revan can just sit this one out.
Older Sith ftw!