Owowowowwow...
One of the best flash games i played in the last years. A true masterpiece. REALLY great...
Its great in every point. I cant find any way to improve it.
Maybe try to enable right click if possible (dunno) to make it more like warcraft? The kinda easter eggs were great ! War2/3 quotes, movies quotes (jumpers :D) and you designed SO MANY MONSTERS, we only see them once sometimes..
I d say maybe make a level pack ? I m sure u ll have plenty of success on app stores. Try to get it on xbox live etc if you can. Why not on steam...
Regarding balance, lightning masters are overpowered. As soon as i got them, with a full upgrade focus on mages, they ruled anything to the last level ( i m not talking about archimage which are a bit crappy. Better make more lightning masters ).
Also, hero spells... are useful in early game, but arent scaling well in the last levels. And we lack mana often. Maybe have more mana regen, weaker early spells, maybe better upgraded spells... I found that most of school were useless. Only necro helps a lot in early.
Well ty for the game :) If you need help porting it in other languages drop me a message.