As his group is very close to the Aurios Mines portal, it can be pulled to the portal such that those guards outside the portal will help fighting. However, they will only do so if you are in favor of the Luxons.
A little trick to players who want to farm his staff is that, Milthuran will only drop his staff if he has it with him. To check this, one may aggro him first and then run away. If he switches to his staff or a wand, then there will be a chance of dropping the unique weapon. Else if he only wields his sword, the staff won't be dropped. He may still drop the staff even if he then switches back to attacking with his sword.