And Maul ? Maul was destroyed by Sidious in a lightsaber duel. Sidious was moving his blade so and precise around Maul that Maul would have been cut if he had moved a single muscle. Still...the same Sidious that had his ass handed to Mace Windu in a lightsaber duel.
Ass handed, umm, Mace was fighting as hard as Sidious. Sidious could have overwhelmed Mace with Lightning or another Force Power. ROTS Anakin is about hmmm, maybe 86% of Sidious. Vader might be around 86-95%. Mace is around 90% of Sidious. Therefore, Vader is basically on the same level as Mace. Mace MIGHT win (it's possible, though I say they're equal) but Vader himself can deal with him for a good time, and with Maul they easily overcome Windu.