The third game is more well-thought-out as a game; it's easier to predict its further development. The fourth game has its own quirks, for example, the number of enemies increases 4.5 times depending on the difficulty level, compared to 2 times in the third game, which sometimes slows down the start very much. But this is more of an imbalance than a flaw. Imagine a real situation - cavalry attacks infantry, and they form a tight formation and raise spears - some of the cavalry will cut down the infantry, and some will be impaled on the spears - that's simultaneous attack!
Added after 13 minutes
I think we're not talking about the moment of the attack. In any war, they won't wait for the opponent to deal half damage to a unit or even kill it with one blow. The first strike, as a property, looks better. In itself, it is a powerful tool in combat.
And still, I can't agree with you.
I suggest we end the argument.
I would fix it, but you wouldn't.
Since I don't know how to do it, and there probably isn't a mod for it, I hope that some like-minded person will still do it. Heroes 4 is a very interesting game, but unfortunately, I just don't understand this combat system. And I'm not the only one.