Well. This is a thing that happened.
Talking with some people in the chat, the AI in FFT will not target empty spots or take into consideration what is around. So even if I didn’t move my Black Mage before attacking  and just left hi there, the battle would have been won anyway.
Thanks, Final Fantasy Tactics. This might be the first time you’ve done something nice for me.
An attack which was a bad call, because it could have triggered Algus’s (Argath’s?) Auto-Potion which would have not let the spell kill him. ↩