I'm not sure the Empire from Star Wars counts. Even accepting Force-users as equivalent to wizards, the Emperor and Vader were the only "rulers". The Moffs who administrated and Admirals/Generals who led the armies were generally not Force-users, and the Emperor's Hands and similar groups were tools of the Emperor, nothing more. It's even implied in a number of books that once the Emperor became immortal, he was going to kill Vader. Magocracy requires more than one wizard. Most of the other times the Sith ruled counts, though.

How is the Government in the Bartimaeus Trilogy corrupt? Highly unfair to Muggles, certainly, and attempted overthrows every book, but I don't think any of the magicians were ever actually bribed succesfully.

There is an entry for the Tevinter Imperium in Dragon Age Origins, and later an entry for the Tevinter Imperium in Dragon Age. Considering they're the same thing, this is a problem.