I like the Warmaster approach to magic users. Most are slightly less effective leaders than their warrior equivalents, the heroes. Like heroes, many of them have access to monstrous mounts that allow them to fly or to boost their combat ability or to cause terror in their opponents or, in the case of dragons, all three! They have a limited selection of spells that are significant but rarely battle winning.
I would be included to follow the WM / HoTT approach to ‘battle’ magic at this level of game. Nothing to specific to an individual but more to aid your side or hinder the opposition. Not forgetting some kind of ‘fireball’ spell 😉