Revan's actions during the war led to his fall to the Dark Side.
Now as to what I would do in this situation if I were the Jedi Grand Master.
I would work in conjunction with Republic heads of the military to analyze the attack plan of the Mandalorian. Using the information that we gathered through meditation and the attack plan of the Mandalorians, I would create a blockade to protect the systems that the Mandalorians are attacking most ferociously. I would then put small groups of Jedi on these planets and two Jedi per military fleet, but only as advisors and fleet commanders. They would also command the ground forces from the safety of the fleet*.
Once the blockade is set, I would then move the Republic fleets to systematically take system after system, slowly but carefully. Eventually, the Mandalorians would be routed and defeated.
This approach would allow the Jedi to fulfill their role as peace-keepers, while protecting their numbers from death and the Dark Side. For the war with the Sith Empire would be won in the Force, not with weapons and starships.
But we do agree that the Jedi could have acted differently.
* Safety as in safety from the Dark Side and the trappings of war
This sound likes a sound course of action, why weren't you on the Jedi Council! What would you say to Jedi strike teams (similar to SWTOR) striking out at key Mandalorian targets so a Republic victory could progress more smoothly? I feel that in such a format, and detached from the frenzy of full scale war (as well as not being in a position of command, they would simply have objectives to complete) and would prevent fall to the dark side. And didn't they do this in the Clone Wars? How many episodes are about Jedi teams taking out targets, performing rescue missions etc. rather than full scale war?
As for your first statement however, partly true. Revan's actions did lead him close to the darkside. But it was Malachor and meeting the Emperor that gave the final push. If these events were prevented, his fall would never have happened. In fact I think the main reason for his fall was the True Sith threat, like Kreia said he never 'fell', but felt it was necessary to become a Dark Lord to reforge the Republic (and he was brainwashed by the Emperor
- people seem to forget this). If he had never discovered the True Sith, he would have no reason to fall to the dark side, because that would mean turning against the Republic, and Revan would not do that without good reason.