I liked it a lot. It's very complete and surprising amount of content. The world permanence makes exploration and progress very enjoying.
It has a somewhat steep learning curve, some instructions on how each class works would be appreciated. The traps where you use a lever and get stuck are not fun, because there's no way you could predict it. I managed to get to the second floor, but each new restart from there left the last door closed and I had to go all the way to open it again (for some reason it doesn't persist as the others did, I guess it's a bug).
There was an enemy down there that I couldn't beat, I don't know if I need a specific team or just spam damage between runs until it dies. Anyway, I was frustrated to open the door again after losing to her. Random encounters get a bit annoying when backtracking. Also, I felt the first levers section was a bit long: maybe a bit less of them until you reach the door section may help with the pace.
I also feel you could do a strategic cut on scope (maybe some characters and enemies) and it will feel very similar, giving you more time to polish a bit those edges.
But overall I like it a lot (and got me wanting to do something similar, I love the genre). Great work!