Jude is making a point about not speaking evil of dignitaries.Over the body of one of His own prophets? Really? That's the explanation? And what about the "dared not" part? Because in Job Satan is given strict parameters by God as to how far he can plague His servant. There is no disputing or limitless authority given.
And he used Michael as a prime example... who although is the archangel did not revile Satan when disputing with him over the body of Moses. Michael only said to Satan what God said to Satan to his face... the Lord rebuke you.