Level 9/10 enemies have 300+ magic armor (and I've seen it as high as a ridiculous 800 on level 11 enemies), and I don't know what my mages can contribute to a fight other than buffing my physical attackers.
Have you beaten the game yet? Later on, it gets insane. Enemies start having thousands upon thousands of armour, at least on Tactician they do. Never played the lower difficulties.
Best ability in-game is
Overpower, it's seriously great. Larian really does love their Warfare. :P