Valid points. Although we want the battle to be as balanced as possible when a player is using items and heroes, it is very important that the challenge and the rewards are equally balanced according to the difficulty chosen.
We will proceed with the following remedy:
1) On Easy and Normal difficulties, the AI will never have more units than the player's army. It is quite discouraging to play on Easy or Normal and face total annihilation.
Maybe we were too harsh here.
2) On Hard difficulty, the AI may have up to 3 more units than the player's army. It is significantly lower than the current status which was up to 10 units. The gold reward will be increased.
3) On CO-OP, the AI may have up to 3 more units for each player participating. Again, this will be significantly lower than the current status. The gold reward will be increased.
4) On Nightmare...well, it is nightmare. No changes there, in terms of AI composition, BUT we will increase the gold reward.
Finally, we will decrease the APs value of Heroes, as they may be a bit "over-valuated".
The above changes will be done with today's update.