Just finished my first playing session, so here are some raw reactions.
First off, great job shipping on the beta and thanks for being open to feedback!
I loved the concept and I feel like this game is delivering on much of what I hoped with the kickstarter. Awesome work! That said, I ended up rage quitting after loosing all my heroes for the 4th time in a row and a key keep. I understand difficulty is hard to get right, so here's my 2 cents to help balance towards challenging but possible.
1. There are too few "easy" battles at the beginning.
I had heroes dying of old age before the 3rd battle and none of them were very experienced. By the time exploding enemies and bulwarks came around my heroes were not even close to ready. Of course, with each region only able to lose three times before being lost forever and with the attacks coming two at a time, you can't really add any more. So perhaps consider having the initial attacks come 1 at a time for a while to provide good "breeding stock" and experience gathering. It would probably also be good for the heroes to start a little younger.
Alternatively have the ability run "sorties" into enemy territory to gain equipment and xp.
2. The enemies get too difficult to fast.
The enemies go from the seeds to bulwarks awfully fast, and the keep piling them on and the adding that seed mother THING. When I met the first bulwark it wiped out most of my heroes without even so much as blinking. I admit, this is complete noob land, but even after figuring out the basics of a bulwark I couldn't do much to defend against them and by that point I was fighting 2 to 4 at a time. (and losing).
It seems each battle is something like 10 times harder than the previous battle. It be nice if it was a little more gradual. I don't mind hard, I just hate impossible after only a few rounds.
3. Screw the bulwarks
Or not, that sounds painful. I'm playing after you reduced their hp already, but it's still far too high for my heroes. I think my alchimist was at an 8 or something. This means my cabers have to get 3 good turns of hits in kill the bulwarks. With missing thrown in the mix, I'm pretty much guaranteed to lose one hero per bulwark, usually 2. Once there's more than one of them my heroes never one. I'd fight the first group of bulwarks and have one hero left and then meet 2 more.
Maybe in later parts of the game my heroes could be strong enough, but I couldn't get heroes strong enough because they kept all dying. They play like they should be the big bad of a level. 1 per level. Not 4+ like I was getting.
Oh, and whatever that mother-seed thing was it completely wiped out all my heroes the first time I saw it because there were TWO of them shooting at me from off screen.
You may not have enough monsters done to allow for more gradual, so maybe there can be leveling on them, so say a level 1 bulwark has less hp and less piercing than a level 2?
3. The keeps don't produce enough heroes in the early game (and probably later too)
I get that they can only breed so fast, but my hero stables got pretty empty pretty fast. I could not build keeps fast enough nor did they breed fast enough to replace just loss from old age let alone a few bulwarks. A more gradual ramp up would help this as I could get the keeps into baby-making shaper early enough.
4. Bloodlines seem awesome
And the heroes, their stories, and relics all grow on me and I start to care for them. Until they turn into disposable single use heroes because the battles wipe out most/all of my heroes each time and even after I see a few too many death from old age notices flash by.
So to fix, well one, I'd rather heroes didn't become disposable. Not sure if I need stronger heroes or weaker enemies. Two, it could be nice to pause a little more at births, graduations, and especially deaths. Maybe a cutscreen of a funeral at a hero's death that talks in pompous language about their great achievements and children/grandchildren.
5. The battle UX could use some tightening
I didn't realize I could move the camera until right before I rage quit, when I lightly smacked a bunch of keys on my keyboard. I just learned I could chose where heroes attack from on this forum, and really wish I had a "defend in place" or "wait" option. The last may exist, I just haven't learned about it yet from the ux.
That's my quick reactions. I will play it again and see if I can get stronger heroes earlier. That may help a lot. A more gradual ramp up would be great. XCOM seems to have that down pretty well. It gets harder, but doesn't get impossible unless you've made several really bone-headed choices.