1. Can we put an end to the argument that Sion getting repeatedly struck down by Meetra is a poor reflection of his skill?
He doesn't have the same need to defend himself as others do simply because he's not as vulnerable as they are. Not defending himself adequately would only be a poor reflection of his skills if he had the same defensive priorities as other Jedi/Sith, but he doesn't.
Plus, KotOR 2 Meetra is an entirely different animal to the delevelled one we see in Revan. Clearly Drew didn't have the respect for the KotOR 2 source material that he should have. But as per KotOR 2, Meetra has a far more impressive resume than Windu or Dooku.
And also, canonically Sion was in love with The Exile, so there's that as well.
2. Shatterpoint wouldn't have any physical advantage over Sion at all. Mace simply cannot do anything above and beyond "killing" Sion, and that is exactly what Sion cheats: death. Shatterppint would only work via a situation, which is simply unlikely to happen.
3. Mace and Dooku are really not that impressive in the grand scheme of things. Sion has achieved far greater heights than almost anyone, let alone these two, and Meetra's exploits in KotOR 2 was the stuff of legends. Team 1 is extremely outmatched here. It's only movie bias which would lead people to think otherwise.