I'd still like some of the following issues to be addressed:
1. The Dead are a mess as far as the AI is concerned and present NO challenge on any level. I think they can be fixed with some balance. Giving them some added population growth early somehow could help.
2. Outposts need some work -- the AI cannot upgrade them at all as they are implemented and they need to be fixed so the AI can use them. Simplifying them seems appropriate--perhaps just make the Outpost upgrades automatically apply once the appropriate tech is researched. I always feel like I am cheating when I use them, and it makes the game feel incomplete.
3. Roaming monsters is at least partially broken. Monsters should not wander from Wild lands area, nor should monsters wander off of loot nodes in wild lands area. It makes it far too easy for the AI or players to run around looting the areas without technically clearing the zone.
4. AI units often end up moving multiple units on to the same square. I'm guessing this is due to the simultaneous processing of certain moves, but it is very confusing to new players.
5. Some balance to champions to help them late game. I like that they have given the late game champions some boosts in the current 1.6, but I think more needs to be done. I think we all hate having so many useless champions late game--there just isn't enough experience to get them all leveled up. I'd suggest that Adventurer's Guilds be buildable in all cities and perhaps boosted to give 3xp a turn. In testing I boosted the output of the single Adventurer's Guild to 5xp and it felt pretty decent. Allowing them to be built in all cities makes it easier on the AI. An alternative would be simply to allow all heroes to gain 1xp per turn regardless of what they are doing, and allow the Adventurer's Guild to be a special building that provides an addition 3 or 5 XP to garrisoned heroes.
As it stands now, I find that in mid-to-late game I have a bunch of fairly useless champions that only serve to reduce city unrest. This makes the mid-to-late game rather unsatisfying as far as heroes are concerned, especially considering the game is "Legendary Heroes." If I'm lucky I'll get governor champions which will have more use late game. I think the main problem is the result of a few issues: 1) Champions/Heroes take a fairly long time to level up, and in late game there are far fewer mobs to gain experience off of than earlier in the game and you generally get experience at a slower rate when fighting opposing sovereign armies; 2) Trained troops in the mid-to-late game are generally very strong compared to all but the highest level heroes that are carrying the best magic weapons.
Another suggestion would be generally increase the power of looted items across the board. Looted items are NOT useable by trained squads so they should be at a higher level to reflect the heroes' better abilities with items.
Finally, you could also take a cue from one of the mods, and give Heroes a base increase to stats, including attack, each level.