Mages won't melee attack?

[Gothmog]

I'm trying to cast Phoenix Pyre on some Mages of mine and then sic them on the enemy. I set their orders to 'Communion Slave' then 'Attack Closest'. I then have two masters chain buff them with Personal Luck, Fire Shield, etc. All that goes smoothly, except my mages never actually ATTACK anything. They just stand there.

What gives?