Mages – their development.

Summoning Magic (elementals and phoenixes are very useful), Chaos Magic (I really like casting Meteor and Rain), Logistics is highly desirable (since mage heroes have low movement range), and Luck can also be useful.

I think Chaos Magic is completely useless for Academy heroes, except maybe at the beginning of the game, and even then... Summoning Magic and Light Magic are the only ones they really need, and they don't need Luck, it's better to take Defense, because Luck can be obtained through minor artifacts, and that will be enough.