That is true. But then again that was more his legacy in death, in life he his saved the Republic from destruction at the hands of the Sith twice. But yes, he new Sith philosophy was a major contribution to the Sith Order and its eventual triumph over the Jedi.
Agree with all of this except Revan doing more as a jedi with his legacy, since his teachings via holocron as a sith are the core of what Bane used to create the Rule of Two. Without them there would be no Rule of Two.