The Power of the Daleks - S4-E3
Deliberate mistake: During all the animated parts of "The Power of the Daleks" in numerous shots various illustrated character's such as The Doctor, Polly, and Ben have their buttons, pockets, patches, etc, flipped to the opposite side, sometimes even within the very same shot.
Answer: In 'The Five Doctors', three separate Cyberleaders are definitely used. So it's likely that Cyberleaders are like unit commanders, of which a fair-sized army might have several.
Daria Sigma