I think that if they really tried, Palpatine would have been dead.
Look at it, Palpatine wasn't very fast. When he went to stab what'shisface Agen Kolar, it's shown that he pulls back and stabs in. That's more than enough time to block and defend. If the four Jedi Masters were to circle him, Palpatine would surely have been dead.
I really doubt that THOSE four Jedi Masters were weak and complacent; Kit Fisto led an assault on Mon Calamari, and single-handedly destroyed a giant beam thingy. (A LA Clone Wars. Canon, you know.) Saesae Tinn led the space assault in many missions. Agen Kolar...well...I don't exactly know what he did, so he could have been killed off.
But we're talking about members of the Jedi Council. They would not be on the Jedi Council if Yoda and the rest thought that they would not be able to be more powerful than regular Jedi Knights.
What shocks me is that Anakin WARNED the four that he was dangerous, and to be weary. Plus, if all four Force Shoved him out the window, that would be the end of him.
They being stoic was just a way to get to the Endgame; GL should have thought of something better. D:
EDIT: And a side-note: Anakin Skywalker (Darth Vader) was the most powerful Sith, not Palpatine.