[Norfleet]

Actually, microing the assassins to do that won't work: What if they assassinate somebody, and are discovered on the same turn? Then they'll perform their assassination properly, since they have the right orders, but then try to "assassinate" an entire army.....and be killed.

It's a no-win situation, unless you're using assassins that can cast returning, in which case you can script them for "Disintegrate, Returning", in which case they'll always fire a disintegrate, then vanish.