[quote=Lucius Cypher]
Khan keeps the teachers in line but also has to play politics with the college. He doesn't have time to deal with the affairs of a mere guardsman. Let me narrow it down for you: who is the on who manages the security and protection of the college?
[/quote]

The Guard captain is in charge of the militia, Tyrael just manages the demons. I doubt Khan would allow someone like him actual people under his command.