i agree in all 3 points here. But the easiest fix is sure the first one (ability to 10/10/10 is the easist way)
2nd problem are problems of the engine, i dont think this is so easy to change this
3rd perhaps battletime depend on the power of armies - for <200 armies there should be ok with < 15 min. (sieges can go longer)
for the 2nd and 3rd problem perhaps a lttle bit from total war
on the startpoint of the defender zone of control - if the attacker control this for 3 min. (he has more men then the defender in this zone) he win.
so if the attacker dont attack -> after 15 min. battle ends with defender win
if the defender run away -> after the controling of zone 3 min. ends with attacker win
but the most gamebreaking is the 100% immunity in that very long time.
p.s. the game is really amazing, so pls fix this
p.p.s i only run in circle if i see the One-Man-Hero... i wouldnt run away and "stand my man" against a normal army or a heavy hero, which could be damaged.