Air already has plenty of combat magic, unlike water.
And the conversation about the third level didn't start for no reason. Some spells from the 3rd tier can be moved to the 2nd (Earthquake, Teleport, Fireball), and some can be moved to the 3rd (Blindness, Lightning enhanced in damage). The idea is raw, of course, but it's worth considering in this direction.
Well, and the fact that the starting armies need to be balanced, that Brogh and Tiraxor need to be nerfed, that's a given.
Added 7 minutes later
Fire will only make sense to take for Berserkers.