First off I think the game is definitely getting very good. Other than the obvious balancing things and extra content for more interesting options I had a couple suggestions.
1. Make all world level improvements require production from the closest city. This makes protecting/razing them more of a big deal and means harder choices for your city build queues. (If you don't do this then at least make it so that they never take up the city build queue even if they are adjacent to the city as the inconsistency/metagameyness of it is driving me nuts)
2. Rebalance weapons (and armor) to give them meaningful differentiation and reflect real world weaponry. I absolutely hate the fact that you guys gave piercing weapons armor penetration. It makes no sense to me at all. And it's maddening that the first decent weapon you get is also your armor pen weapon meaning that you can easily use spears on all your units for the whole game (it's what I typically do). In the real world the weapons people used to counter heavy armor were typically heavy swinging weapons with points ie warhammers. I think a few simple principles would be good to follow.
Early Blunt (clubs, maces) - Very cheap, very poor attack power, relatively effective against all but plate armor, ineffective against most creatures
Pierce (spears, bow) - Slightly more expensive, poor attack power, average effectiveness against armor, barely scratches plate, effective against high defense creatures
Sword Type Cutting - Relatively expensive, excellent attack power, poor effectiveness against armor, barely scratches plate, effective against most creatures, give dodge bonus based on level to reflect parrying
Axe Type Cutting (Two handed swords here too) - Slightly less expensive than sword type, better against armor, dodge penalty, accuracy penalty
Late 'Blunt' (warhammer, maul) - Slightly less expensive than sword, armor piercing, dodge penalty, accuracy penalty, largely ineffective against creatures
Now I haven't thought out the exact mechanics that would accomplish this ideal but I think most of them could be fairly obvious. This would give us real incentive to have different kinds of troops. For example swords would be good to give to defensive units as swords are a good defensive weapon and do decent all around damage. Plate armor should be crazy strong and terrifying if you don't have late game blunt weapons to counter (also it should be possible to reduce damage to 0 esp with plate). Spears need some kind of special ability to distinguish them I think (besides armor piercing) something to reflect their ability as a standoff weapon (I want to be motivated to make phalanx units).
3. Tone down the experience reduction for heroes/army. It is too harsh and basically means that I never am willing to put more than one hero in an army. Perhaps a gradual reduction where 2 heroes get 75% xp each, 3 heroes get 66%, 4 heroes get 50%? It really kills the adventurer strategy. I just feel like you guys went to far in nerfing heroes. I've yet to get a my channeler to level 10 even though I fought most battle with just her and I've fought 3 major wars and done a lot of adventuring.