2 things that bother me right now:
-tech tree is too big. eg. there's techs like Weaving, Irrigation etc. that serve too small individual functions and would benefit from being mashed together. There's also a vast quantity of magic techs; personally I feel it'd be better to move spell progression somewhere else.
-Great People are really unexciting. Assigning promotions is a mundane, repetitive choice and generally your best bet is to level a GP as high as possible in one area, meaning you make a single decision at the beginning of the GP's life and don't really change it.
The importance of passive XP is kind of unexciting. I want to make my GPs awesome by making them
do stuff.
This next bit is more of a suggestion than a balance change. Better to put it here than clutter the place up with another thread? ^^
- Remove passive XP. It's boring and reduces the value of the active XP rewards. You should get XP for doing stuff!
- Develop sources of active XP. Writing tomes and building wonders is a good start. Maybe you could introduce some more, for some kind of ruins that Sage can explore for XP Archaeologist style. Maybe add some risk/reward options eg. Druid going on a Spirit Journey in a forest at the risk of losing their mind or a Sorcerer summoning a demon for forbidden knowledge with the risk of losing control.
- Separate learning spells from promotions because that doesn't fit with the decreasing rate of level-ups as a unit gets higher level... my most powerful thaumaturge should not be the one who has the most trouble learning spells. Make it cost mana or take a certain number of turns to learn a spell if you want to limit the number of spells each GP has.
- Turn Promotions back to a more Perk-like form performing interesting and unique functions. eg. "Rapid Cast" would give +25% cast rate, "Magic Carpet" would give +1 moves and ignore terrain costs, "Expert Healer" would act like the Medic promotion.
Choosing between these would be more fun than adding attribute buffs.
- Increase attributes/modifiers separately from level. My suggested system; every turn, each GP has a percentage chance of (20*level)/[highest modifier] to increase a modifier of the player's choice. This makes passive XP unnecessary by making levels no longer necessary to produce decent GPs, yet still directly rewards a GP for the levels they have earned with active XP with an increase to the rate they gain modifiers. Since the rate is only reduced by the highest modifier the player is encouraged to develop a range of abilities for their casters instead of stacking one modifier as hard as possible.
- Leadership mod should no longer be a thing because it encourages further specialisation of GPs into boring single use units instead of putting some thought into how to make optimal use of any GP at a given moment. Maybe a GP could give a bonus that is defined by and scaled to their highest mod at the current time?