Auto-translated
Pandora, I've been following the discussions about Heroes 4 closely and realized that you have a lot of experience with it, but in this case, I still agree with MagicMan. Surely, you can't really manage to use spells from all schools of magic in a battle. I don't think so. At least, I don't remember such battles in my games. But a developed "Combat" skill, firstly, provides magic resistance (which is quite good against enemy sorcerers), and secondly, increases defense, which allows you not to pay too much attention to the physical attacks of enemies. Personally, I think that two magic skills are quite enough, or a maximum of three – if you want to create an archmage, although I would prefer tactics instead of the 3rd magic skill.
I'm not claiming to be an experienced player at all. I just always talk about MY preferences. In campaigns, I almost always develop all schools of magic. Almost, because sometimes there are heroes with initial "Combat" or "Tactics" skills.
In one battle, I certainly won't have time to use ALL the spells. And it's not necessary! You need a combination, you see? One magic skill has something, the other has something else. It's very useful when there is room for maneuver. So that you can respond to the opponent's actions not with a stun, but with an action.
And I don't have a clear, specific scheme for when I use what and in what (specific) sequence. It all depends on the situation in the battle, which is unpredictable.
I'll try to describe some battle in detail sometime. I'll specifically record all my actions and the opponent's actions.
