Here's a brief opinion from a player of the "single-player game."
The significant influence of several artifacts and hero classes stands out.
For example:
Staff of the Netherworld
In my opinion, there is no alternative. And the difference between playing with this artifact or without it is winning a battle without losses or losing.
Or, for example, the Elf race:
Why have "Ranger" and "Druid" if there's "Avenger"?
He has all the skills to enhance the army + "Dark Magic" (general slowdown) and "Destructive Magic" ("Master of Ice").
What can the other two classes of this race offer in comparison?