I haven't played a lot of the game yet, so I might be wrong at some points.
1. I agree with mana production. After some time I get to a point where I have to put the game to background to get some mana produced.
2. Other thing is that villages seem a bit unbalanced, when they come attack me, they die really quick. When i attack a castle it takes a lot of attackers to just get through the door. Iron golems are better with this, cause they die more slowly. However they seem to be able to block any number of my humanoids or beasts at the door.
3. Also can i get prisoners when attacking ? They only seem to surrender when they attack me
4. I wish there was some super-aggresive enemies option, or enemies growing in power with time. I enjoy defending my dungeon, but right now there is very little risk of being overrun.
5. Some ui improvements would be nice. I especially loath having to shift click drag to get square area, shift seems unnecessary, just click or drag would be enough. Also maybe mapping zoom to scroll wheel would be possible.
6. I tried playing adventurer mode, however for now it seems quite dull, ended up walking around for some time with nothing to fight with.
7. Gold is useless for keeper atm, maybe it would be better if elite monsters would require a gold upkeep. It would give some incentive to mine it.
8. It's true that resources can be easily used up, especialy if you get unlucky with mapgen. Maybe deposits should have more ore in it, but take a lot more time to dig. I Haven't had problem with wood though.
9. It is weird, that humanoids don't have to eat at all. I think some food production would be nice addition. Or maybe pillaging villages to get food.
10. Also there should be some system for monster moods. Some extra equipment to keep them happy. This could also be dependent on what different monsters live around them, the lightning etc.