There has been a lot of discussion in the forums about how overpowered hero units become vs regular units.   

One reason for this is that hero units gain abilities, etc as they level up and can find new equipment as loot or buy new equipment to improve both their survivability and their attack strength.

Regular units level up but  gain only some stat improvements.    To improve their armor or weapons they have to pay for an upgrade.     The problem is those upgrades are prohibitive.    I recently wanted to upgrade a unit of 5 from leather armor and a hatchet to chain armor and a fair sword.    The weapon upgrade would cost 1400 gp and the armor upgrade 7700 gp!  Higher level improvements, when available through research, are much more expensive than that.  

In addition regular units cannot pick up loot - if there is a hero unit in the stack they get to pick up the loot.   If there is no hero unit the regular unit cannot pick up loot from empty sites or from battles with monsters.

This means over time our experienced regular units fall behind the hero units and are easier to kill.    Of course we can then raise a new and inexperienced unit to fill the gap.   They have the right weapons and armor but their stats are so low they too are easy to kill.

I suggest the cost of regular unit armor and weapon upgrades be reduced significantly so that they can better compete with hero units.