Yeah but what does that matter?
Give a force user a weaker fighter and he could still take out many superior fighters. These guys were damn force users, yeah their capitol ships couldn't easily take out imperial capitol ships. But the Rakatan could easily create 10x as much ships as the Empire could ever dream off. Imagine a few droids in those and set for ramming speed, the Empire would go down and pray for mercy as the first load of droids hits.
They don't even need to know the weakness of the Death Star a 100 ships crashing on it would be effective as well. Also you have to remember are incredibly smart i'm sure they would adopt their technology to that of the Empire, and its obvious that the Star Forge can create other kinds of ships, so if they capture a Star Destroyer or a SSD (which probably wouldn't be to hard) They could start creating those things.
And I'm not so sure if the Rakatan capitol ships are weaker now that I think of it, the ships Revan used were not those that were originally created by the Star Forge during the height of the Rakatan Empire. After all the ships Revan used were not powered by the force, so it had been changed. How much more powerful would those ships have been if they would have been powered by the force? Imagine the power of one ship powered by god knows how many force users.
Then you have the ground battles, there is just no way the Empire could ever win a ground battle when you are facing a shit load of force users. Nobody could ever pull it off. The only one's that stand a chance against the Infinite Empire are the Ancient Sith, and then only because Ragnos can probably blow hundreds of them away and Sadow can start throwing stars.
And even then we don't know the power the Rakatan wield, but its probably pretty good because they had practiced for a very long time and had many years of training. So all in all, the Infinite Empire would slaughter pretty much everybody with the possible exception of Ragnos and his Sith.