Tenebrous has to be massively above Dooku for Banite scaling to work. Plagueis may have been an anomaly, but there are some documented cases and presumably more where the apprentice kills the master in single
combat, often before their prime. Tenebrous himself thought he and Plagueis were passing some line in their order's history, and maybe he was delusional, but Plagueis didn't seem to disagree and his own power speaks for itself.
Tenebrous is probably above or at least near Vader, and thus beats Revan, with his saber skills breaking any reservations.
Originally posted by NewGuy01
Is it not believable?
Personal, it falls perfectly in line with the overall narrative.
I believe both Plagueis and Palpatine where both significantly above any of the Banite Sith. With the gap between Damask and Tenebrous resembling the one between Darth Vader and Sidious by RotJ.
Well, that's my thoughts on the matter at least. We'll never know for certain given the window of Legends canon is shut for good.