Combat spells are overpowered
I think the combat spells are overpowered in Elemental. Even without a shard the damage is based on the characters Intelligence score and this results in 0 - 15 points of damage (Intelligence 15) at the beginning of the game.
You need only Intelligence for spell damage, Wisdom to cast enough combat spells and Constitution if something should go wrong for some reason. As soon you get area effect spells and multiple shards units become nearly useless.
A solution would be that the AI (im playing on normal) attacks multiple towns at the same time. In that case the character can not defend all cities with full mana.
Another solution would be a reduction of the base damage of combat spells to Intelligence / 2.