Heroes 6 - Discussion

It's unlikely that your version is correct. Why? Here's the answer:
1) The spell, in theory, should work for several rounds, just like before, right? Let's assume that's the case.
2) With this system, the creature will attack the nearest unit, and then move and... it will reach the enemies, receiving a "bonus" in the form of a double attack from the opponent, directed at the opponent's troops.

So, in the variant you proposed, the spell will cause more harm (if the opponent isn't an idiot) than benefit.

Added after 43 seconds

The mage cast a fireball over an area, but the damage won't be dealt in the turn the spell was used. The creature will be able to exit the area of effect and only then will the spell deal damage, when all units are outside its area of effect.

That's exactly what I meant.