Good point, but Pall did have a great blade and that is for sure, it was supposed to have destroyed him and legendaric. Meaning his blade is damn powerful and he created it, so he was a weapon master. He was also burried on Korriban. Now a weapon master that has a tomb on Korriban doesn't have to mean a lot, but when you see his tomb it does.
So he was improtant to the Sith thats for sure, then he manages as one of the few dark side people to return as a ghost or whatever, and not just a few days later but many years later. Meaning he also had a great knowledge of the force, he was a force user thats for sure because he was a fallen Jedi. Now he was a fallen Jedi that has a tomb on Korriban, was a great Jedi Master and still manages to return as a ghost many years later. Meaning he did have a great control of the force.
Yes its all based on lose arguments but i'm getting all i can get here, and i do believe Pall is incredibly powerful, because otherwise he could not have done anything like that. Maybe not as poweful as Revan and Exar, but powerful enough to beat Sion. Exar can take out Sidious then. Maul will die because of Revan and then its still two against one.
Actually i think in this case the team that strikes fastest will win. At least now that i think about it a bit more.
Would Sidious hold Pall and Revan face Maul then Revan would be able to kill Pall and... Nah i'm still going with Pall, Exar and Maul