At the same time, there is a strong imbalance in favor of the undead faction's troops.

If you used a necromancer for an hour, then respect, I understand that this is not a very popular tactic, as it requires effort.

it would be better to make potions more dependent on skill than on the number of ingredients

I think the most logical option has been implemented. Potions depend very much on skill, as you can only brew the best ones by leveling up, but even if you are a worthless alchemist, you can put in a lot of ingredients and get a strong, albeit simple, potion.

Rune casting is again a pity to use, resources are money

It seems that you can quickly understand that resources are used only for two things - rune magic and exchange for gold on the market. Based on average exchange rates, you can estimate how much one spell costs; I don't remember exactly, but most of them should cost no more than a thousand. And this is essentially the cost of 1 creature of level 4-5. With this arrangement, rune casting is beneficial in many battles.