Let's look at Traya's and Revan's forces more deeply.
Obviously, they're mostly the same people. What changed? Well Traya's are evil and corrupted. Who corrupted them? REVAN.
They're love and loyalty to Revan is what took them to the dark side in the first place. So they won't be turning in this scenario (at least not many of them - 'cause obviously there are individuals who'd turn).
THis is so wrong. Yes, many were corrupted simply because of their loyalty to Revan, but it was more than just old war dogs fighting Revan's war, it was converted jedi. And they were converted by torture, brainwashing and the power of a given dark nexus- chiefly Malachor V post-mando wars. Atton Rand was one such agent for the empire that broke and converted Jedi.
Also, too much value is being placed on the power of longevity. Longevity in a conflict is nothing if you have no opponent to outlast. Remember that the Trayus Academy at Malachor V is hidden. Assuming they hold that advantage here, Traya's assassins can outlast Revan's forces no problem. Also, Malachor V is NOT a practical target for the Republic to engage because of its darkside power and hazardous environment to space craft. Yes, I am aware that WMD's aren't allowed, but the influence of the active, heavy and unnegotiable gravity and terrain of M5 makes using a fleet quite difficult.
Yes, Traya has a fleet, it is the remnant of of Darth Revan's Sith Fleet, and it is powerful enough to engage the Republic as well as TSF and their surprise Mandalorian and Onderonian allies at the battle of Telos. of course, the aim of Traya's fleet, under the command of Darth Nihilus, is to get Nihilus in place in order to feed off of the planet's life force. It can easily be used to engage Revan's fleet in the open and sabotage them from inside with superior boarding parties of assassins. Remember, we're not allowed to use Nihilus, but Nihilus' forces are under Traya's control... If we could use Nihilus, this would be a lulzy 1-sided fist fight.