You don't have to be an archmage! Just Life + Nature will do!

That's enough to start with. And then you can develop it further. For example, Death would be a good addition to Nature... And this is a big plus, that there is development. You don't have to be afraid, as for example, if you first level up a hero's Combat skill, and then, since the game continues, you decide to level up Scouting, you get a ranger. And then what? Where do you put the experience points?

What about griffins? Are they more effective than ungulates when playing... let's say... against Death! Blind a vampire or a skeleton?!

But that, of course, depends on the situation. If you know who your opponent is. But unicorns are also not bad... at a distance. They might lose to Death, but Life will have a hard time with them.