I'm just saying that it is debatable whether or not Mace legitimately beat Sidious there, considering the surrounding context with Anakin.
Either way canon has established Vader as a better lightsaber duelist then Sidious, and "light-years" beyond Maul and Dooku..... And Luke was stated to be his equal. So no, I really don't see a Grievous level fighter and two other featless nothings being able to press him at all. Fodder is still fodder.
And even if Mace is legitimately > Sidious in sabers, so is Vader (and therefore Luke). Difference is that Luke's power also scales to Vaders level, while Mace's obviously does not.
All material factored in, this is Luke's fight to lose IMO.