I think the different tech trees could be better balanced. In my opinion Warfare and Civilization are the most powerful trees, because they give you many different upgrades. Magic, Adventuring and Diplomacy are good at the lower levels, but have not enough interesting upgrades at the higher levels.

The magic tech tree should unlock magical creatures and the ability to change existing magic items.

The adventuring tech tree should be the only way to get magic items.

The diplomacy tech tree should unlock espionage options.