I think this is exactly the kind of situation that GP had in mind. A computer would be undoubtedly faster and more accurate concentrating fire on the weakest stalker, but a human is better at deciding whether to attack now or move into position.

So instead of 'attack this unit,' the player could command his units to 'attack the weakest stalker in range.' Or even, 'stutter step along this path, concentrating fire on the weakest anti-air unit.'