Predictability of the AI.

I've described my point of view; I prefer to play with a single hero. It's just more convenient for me. Of course, the hero needs to be strong. If the hero is powerful, then a large army theoretically makes the situation worse (meaning a large army of weak, rather than strong, creatures). Let me explain: let's say my enemy in battle consists of griffins. My hero knows 5th-level Chaos magic and has 1st-level Warfare skills (making him a level 21 hero). It will be easier for me to defeat the griffins with a single hero than, for example, with berserkers, centaurs, and thieves. Firstly, it takes longer. Secondly, the enemy army will be divided into three groups in battle (because of my army). But if the hero is alone, there will be only one group of the enemy army. And it's easier and faster for me to defeat one group than several.