When I was talking about the combat mechanics, I was, of course, referring to the presence of heroes on the battlefield. And I only mentioned Horna as an authoritative example. I doubt there are any calculations on paper, although I don't think anyone would stop us from repeating them.

Mathematics doesn't recognize authorities; it only recognizes the rigor of arguments and transformations, which is why it doesn't always get along with models.

If we take a standard situation from the fourth game: 3-5 heroes and 4-2 monsters. Then, in principle, you don't even need to calculate much; the number of possible behaviors in combat is simply overwhelming.

You call it standard? Maybe on the narrow maps that are popular among hardcore online players, that might be true, but even for the standard maps, I doubt it. Or has the situation changed so drastically in the Versus mode? Well, let's leave that aside. From my experience communicating with "trash talkers," I know that for most of them, the world boils down to 3-4 templates and a couple of variations in the rules, and arguing with them is pointless.
If you have 4 heroes with magic and three types of monsters (and even better, each with their own spellbook), then it creates the illusion of a huge number of options, but it's only an illusion because, in reality, the choice for each unit will not be too great. When comparing the third and fourth games, it can be said that all the options from the third game are, in principle, also available in the fourth, but the reverse is not true. Compared to the fifth game, only various kinds of "potions" stand out, but the theory of combat in the fifth game is complicated by a much more developed system of skills. That's why I said that I don't know how to compare them in terms of complexity on the battlefield.