Super helpful, and in-depth feedback. Really appreciate your perspective on it, you clearly know the genre well - especially given you crushed your first run!
If only you'd rested at the campsite and transformed Mystery Essence, it becomes a fairy wisp summon ;)
You're totally right, balance is going to be a huge undertaking. We're gonna be relying heavily on data, and there's thankfully a ton of dials to turn to balance stuff, but it's likely always gonna have the potential to get wacky given the number of possible interactions and hero/card/gem combinations.
Regarding difficulty, it's a tough one to dial in for the demo, given it's only the first act, and balance is most definitely a work in progress. We hope to implement something akin to the Ascension system to provide difficulty progression in the end, albeit with a twist to serve the party based gameplay. For the time being, empowering only provides a modest increase to power, and mostly serves to unlock new cards and therefore playstyles for heroes.
Thanks again, a lot of great insights, glad you had fun!