1. Considering Sam and Ian have access to the script...Lucas could say Luke was a big cat in disguise..../can/, /should/ and /will/ are three very different things.
2. Yes, the lord of the darkside had never fought someone before...he was described by Maul as a fighter of incredible proportions. The hiding your face idea has more evidence than "Errrr......it was the lightning scarring him." Especially when a man who plays the character, gets into his head, reads the script, has access to Lucas and the like backs it up.
3. That Sidious never fought seriously against Mace, that's what it tells me. Especially as the level of his quality fighting goes down. And he doesn't kill Mace-who fails to react to save Kit even, so uber. and Mace's word carries far more weight than any speculation on fans' part
If anything the PT elaborated on Sidious as a genius and mastermind.