They also kind of need to fix the alternative damage they do. Against the player, them doing half damage to stamina/magicka is fine, since our levels of those attributes are typically lower than our health, by a fair margin. Enemies on the other hand, tend to have a near limitless supplies of both, so damaging them is almost pointless.
But yeah, it would be nice if there was a perk high in the Destruction tree that could reduce enemy's resistances/immunities. A few more damage types would be nice too. Elemental for Destruction, light/holy for Restoration, dark/poison for Conjuration, and maybe a typeless damage for Alteration.