llamabeast said:
Well after they attack you they must be visible for at least that turn, mustn't they? So wait till they show themselves again and nail them.
The turn you can see it is the turn you cannot attack it. Because stealth order is executed before magic phase.
Stealth should probably be executed after magic phase so you have a chance at magiking those bastards. I'm just beginning to appreciate exactly how extremely powerful stealth commanders really are.
Can you try assassins against stealthed commanders? Assassins can have trouble against mages, but the odd one gets through to the mage, against astral especially if you buff them with some cheap +MR.