Bet you never guessed that I'd show up here. More surprising perhaps is that I agree with you on most points.
What he does next is shocking however. After the war, Revan finds out that the Jedi Council was correct. The wise masters saw the Sith Empire lurking in the unknown. But Revan couldn't let them know he was wrong.
Interesting take... Might I ask though, what has given you this interpretation of events? The Masters, based on what I remember from talking to Bastila, sensed a darkness more dangerous than the Mandalorians, and received bad omens in regards to Jedi involvement in the war. But nothing ever suggested they knew that it was lurking in Unknown Space, that it was a Sith Empire, or that it was ever anything other than Revan falling to the darkside and dragging his followers with him.
Nor does anything I remember suggest Revan went off to fight the Emperor because he refused to admit he was wrong; I was under the impression that he discovered the Empire, and in his arrogance believed himself to be the person in the galaxy most capable of defeating this new threat.
With the Republic still in shock, Revan leads a crusade that takes countless lives before the Republic could do anything to stop them. Even when they tried, Revan was able to counter their tactics after spending time serving with them during the Mandalore wars.
Worth mentioning that some (such as G0-T0) believed Revan's intentions were to forge the Republic into something stronger, to counter a greater threat. However this is merely semantics as a) he failed, and b) he waged war with no regard for life, civilian or otherwise.
The Emperor then captures Revan and siphons his power. The only thing keeping Revan alive is Meetra Surik's spirit. But even she could not stop Revan's dive into insanity.
During this time Revan manages one of his few successes. Delaying the war (without knowing the Emperor's original schedule, it is impossible to say for how long), and pushing the Emperor to the Treaty of Coruscant.
So what did Revan do exactly? Nothing really.
He defeated the Mandalorians, that's his only helpful accomplishment. The rest of his actions were either destructive or to fix his mess.
Had he not gone into the unknown regions, Revan would never have attacked the Republic. Had he not attacked the Republic, the Republic would have had a much more powerful defensive force to defeat the returning Sith Empire. Failed to see the real threat and the galaxy paid for it.
:- He defeated the Mandalorians and delayed the Empire's return; both of which came at great cost.
:- His obsession with defeating the Emperor/Empire led to all of his other goals (such as fortifying the Republic, whether it be under its own rule or the banner of his own Sith Empire) failing.
:- He perceived the true threat but reacted very poorly to it.
His actions may yet have made the difference in the Republic's fight against the Empire, but this is mainly due to the actions of others (which were effected by his presence), and unintentional side effects of his own attempts;
Although of course, these are hardly to his credit.