Auto-translated
In my opinion, the need for magic depends on the Hero's class. If it's a warrior, then they only need earth magic (general slowdown, general shield, etc.) and water magic (healing). If it's a mage or a battle mage, then they need all the elements. And people underestimate fire for no reason... You can achieve a lot, for example, with a stack of psychic elementals and an expert Armageddon ;) It's just that fire is useful in rare cases, that's a fact. As for my favorite spells: Explosion, Restoration, Clone, Dimension Door, and Town Portal.
Added after 4 hours and 2 minutes
I was just playing SoD as Dungeon. I chose fire and didn't regret it. With 25 Black Dragons, I defeated all the AI opponents. Here's proof of what I said about Armageddon.