I have some suggestion to be considered for improving balance in heroes/troops/monsters. I'm sorry if added some other questions too.
- Heroes leveling up. As the problem is that they grow too powerfull, even if XP gain is nerfed, I suggest this: making the stats growing as a selectable trait. You want a mage? Then, chose magic but no health/attack/etc. improves. You want more healt/attack? Then chose it, instead of other traits. No interesting traits? Then, lets got for health/attack. This can make heroes customization more interesting, variated, and will not become so much powerfull. Mages will rely on magic, with a lot of less stats. Warriors/assassins will have to decide if improve basic stats or select a proper trait. Governors...that is the same: want more stats? then no governing traits. And vice-versa. Governing heroes should give interesting city bonus traits (like +attack/defence trained troops, or resources, or unrest), that makes a excuse good enough to retire them from battle. The Path selection at level 5 is good, and in this case, it could add the stats improvement also, like a "reward". By the way, I miss a Path of the archer too....
I think that on this way, heroes grow up according to player desire (and traits presented), but not so OP. And heroes must now rely more on research to buy better gear, and in troops for keeping them alive.
Does everybody agree in making heroes inmortal, even with the negative traits when they "die" (let's say fall, instead)? As said in other posts, I prefer they may have a chance of real death, instead of always a negative trait. Keeping negative traits is good idea, but as a chance, like saying: "omg, gangrene...but at least, my hero didn't die". Heroes should die, and so should allow a way to recruiting new ones, like a spell of Hero Calling. This spell might go in the Hero research tree, so as better hero recruiting tech, a better Hero Calling. Lots of mana needed for this spell, of course...and maybe a Cooldown to re-use. Or even better: a one use-only, like a scroll instead of a spell, but still requiring mana. That means only 3 hero calling (on level 5, 7 and 9 if I can remember). A good way to replace fallen heroes, or to get new ones if can't find more...With nerfed heroes, probably more will fall, and die. The dodge could be a way to determine real death. And a random in % of negative traits could be introduced. A base + % random, for example: -10% + random% at a skill, instead always a 25%. The random could be determined by the dodge or other skill.
- Troops. I still think the problem for troops is in the Warfare tech tree. It is too closed and straight, not allowing customization. And it takes a lot of research to get the improvements, and to research techs not interested to arrive to the interested. I talk about it in https://forums.stardock.com/432978 With a more open Warfare tech tree, allowing to choose between different attack/defense/mounts/training branches since the begining, it can help in developing customized troops, depending on personal wishes and in the available resources. And AI can focus on some of those branches (like Tarth-archers). Lowering production costs for basic items will help to start basic trooping earlier. After all, if heroes are nerfed in some way, troops at early game will be more important now. Everybody say that at early game, while researching and developing, we can use heroes to make quests and farming. If heroes are nerfed (and they MUST be nerfed), what will we do on the first 50 turns, but pressing Turn-turn-turn...?
- Monsters. If heroes are nerfed like I said, maybe is not necessary too much tune on this. Anyway, I find interesting this idea: Monsters should grow XP, and increase levels as turns goes by. For example, +1 level every 20/30 turns. This allow to get more challenge in later game... The random generated monsters should have leveling upon time too... Combining this with the previous hero nerfing, that might make troops a must have...
- Magic. I find this issue: how is it possible to cast in strategic map as many spells as mana allows? There should be some kind of limit to this... But turning to the magic balance... I think in magic as interdependant or complementary. Many opinions read about magic: from total magic fans, to magic haters. I think that to balance magic, first should balance the previous issues, and then, focus in magic will be easier. Of course, the power of spells must be controlled somehow... I think that Magic Tech tree should be tuned, in the style of the proposed in the Warfare: attack branch, defence branch, mana branch, hero branch, building branch. That can allow a real complement to the Warfare Tree, to the Civics Tree for resources, and to the hero researching.
- Cities. I read a post about how to control excessive number of cities, and big bonus that they can give. I think an easy way to do that is via UNREST penalities. Unrest in far cities should give many penalities to production, and even a bigger chance to rebel. So if you want that far shard, or crystal, or whatever resource, think in having many troops to get less unrest, and/or build a lot of buildings that reduce unrest,...or just build a fragile outpost. That will make troops a must have in expansion games. Many of us want to expand, as it is the only way to avoid enemy expansion after all... but it would give a way to control that expansion, with less productive and more problematic cities.
Speaking of cities, why not thinking in putting independent cities in the world? With their defences, and their growing upon time... It is a source of quests too. it's just another idea.