Issue: the quest to recruit heroes like Mausolos and Ascian (the only 2 I got so far) are rather challenging, and tend to require a hero in the 6-10 range with a decent army.
Unfortunately, the reward is generally a mediocre hero that isn't worth replacing your hero currently leading the army (among other things, both Mausolos and Ascian can't use the full range of equipment and such). And using him with that hero would significantly decrease the XP received. So most of the time, they just go into a random city and sit there for the rest of the game to reduce unrest by 5%.
Suggestion: Make these unique 'heroes' classified as Henchmen. That way, they (and your original hero) will get full XP in the same group, and you will actually want to use them, rather than just sticking them somewhere on the map and forgetting about them.
