I had my first play through on normal, will try again on the hardest difficulty because my first game was a win and that is fairly uncommon for me with 4X games despite being very experienced with them, it normally takes a few playthroughs just to find the units which are a bit OP. Perhaps it is due to the small number of different unit types.
I find Archers and Knights to be the best of the units, perhaps OP? All the melee classes not worth it, Soldier is weak and Sentinel/Pikemen require metal which in my game wasn't that much more abundant than horses so that means the knight was the best investment of finite resources and archers were the best investment of infinite resources. I used soldiers in the first half of the game to be a body wall to stop the enemy getting to the archers but they die too frequently, the wolf enemies hit crazy hard and the melee always died en masse.
Battle Master and Battle Cry are too powerful, when all your units are level 12+ on normal I could easily wipe out a 1k CR enemy army in one turn without relying on any spell casting. Rain of Arrows is pretty brutal on deployed armies and seems to bypass dodge, not sure if that is a bug. My last fight was 5 knights, 8 archers and I think 2 champions. I didn't really craft much. I think some of the components are too hard to come by, most of the stuff I couldn't make through the game, the rare ingredient like trolls blood or ogres blood very rarely dropped.
I ran out of spells to research very early in the game with only a couple of cities, that allowed me to throw a lot more into the sovereign skills, I think i had 25 out of 28 by the end with 4 cities and had enough mana generation to send the doomsday clock from 180ish to zero and still have about 700 mana for the final fight.
I felt the game was challenging very early because I couldn't produce units quick enough to protect the shards and my towns, however, once I got enough improvements going the tide turned pretty quickly, am curious to see how it goes on the hardest difficulty.
It felt to me the game stagnated between the mid-game and the end-game due to logistics, once the border expanded a fair bit I was still largely dependant on one army and some drabs left over running the marathon between cities for defence. I didn't really have the logistics to speed up that phase so spent a lot of time running back and forth trying to put out spot-fires with one army. I could split it in two but would have probably suffered a lot more casualties. I don't think logistics scaled well to the amount of territory you had to cover. By the end I had 2 full size armies but the game was over hours before it ended, the mop up phase was quite lengthy.
Oh, before I forget, those allied npcs just love to sit on my roads, can they be coded to shove off or allow friendly units to pass through them? I will probably be aggressive with them in my next game to keep them off my roads.