I did not understand what you say about "Spirit link". How does it work currently? How it is supposed to work?
How it used to be:
The player applies Spirit Link to enemy troops, and then gains mana by killing them. That is, the mage's mana after the battle is 100% (full), even if all enemy troops are killed only with spells.
I suggest: Spirit Link is only applied to the player's troops.
Added after 22 hours 26 minutes
dredknight
another suggestion: make it possible to choose a city specialization (at the start of the game).