Played the campaign through with the Guardian, Kayla, in her default settings and I noticed a couple of bugs. First, when I researched the Geomancy skill, I received the Revive Land spell rather than the Restore Land spell. I had not yet chosen the Revive Land skill when I picked up Geomancy so it definitely gave me the wrong spell.

Speaking of the Restore Land spell, I think it would be far better if you made this a spell that only affects a single space. If you're worried about overuse of the spell then keep the casting cost high.

The next bug I encountered was that Kayla's Pathfinder skill didn't seem to be doing anything for my land units. They were still paying 2 to enter and move through forest terrain for example.

Similarly, Peregan's Survivalist skill also wasn't working for his army in reducing movement costs. He was the only hero in the army, and while I think it was working when I first choose the skill, it wasn't working later on in the game.