Few more random thoughts:
Military tech tree is too all-incompasing, in most situations you don't even need to bother with other trees. Please condense it and/or spread benefits to other trees. For example "experience" of your units can be stuck into adventuring tree, speed of training, horseback riding, city defenses, watch tower all can be moved to other trees (why are all units have fixed training time?).
What can you do with shards? I can't find any use/benefit from them.
Why are there no standard spells outside of teleport/blink? Resurrect champion, summon familiar, enchant farm ... all seem like ideal candidates for standard book.
Why are you not given starter strategies? First 20 turns feel like "waiting for technology" because of that.
Equipping multiple rings can turn your hero into OP juggernaut.
There is no caster-oriented equipment - no rings, robes, staff that make your hero better.
Why is there so little loot from any encounters with bandits/other heroes?