Just a few random quick impressions about balance.

*  Earth mages seem to get short shrift on the combat spells.  Imbuing them seems like  a waste.
*  Getting valuable heroes seems hit or miss.  In some games I only had the option to hire 3, and in some I had 20.  Obviously both games were drastically differnt outcomes.  In the Total War Games the game has mechanisms for trying to get your number of heroes or generals to an ideal number relative to the number of cities you control.  FE could employ something like that.  HOMM solves it by allowing you to recruite heroes directly from one of your cities if you don't have too many and have the right building built.   FE could cause heroes to refuse to join you because your prestige is spread too thin amongst heroes, On the other side heroes culd show up if you have high prestige and very few heroes.  Just a thought.

*  There's really not a good way to capitalize on the nodes you have been given.  For example I had three heroes with Earth Skills and One with Fire.  But the nodes I had were all life and air.  I just had to say "oh well bad luck maybe I'll find a life mage somewhere",  and play the entire game with no shard bonuses.  Seems sucky to me.  I never got that life mage BTW.

* The rarity of the level up traits cause psychological stress.  I know I want Air Magic III but the dang game makes me feel guilty by teling me that it's COMMON and I'm passing up a RARE trait instead, WTF?

*  I wish there was an option to notify me when all of my units in a city are at full strength for the first time.  I know in elemental they told you every time every unit hit max health that was too much.  But "The Army in ResolynMain is at full strength" would be a nice message to have.

*  It feels to me like outposts should have some sort of maintenance cost of some sort.

*  Before a quest asks you if you want to do combat or walk away it should allow you to see a tiny bit more info about defenders (not just "a pack of spiders").