I think the difficulty is very volatile, on my first run I was easily able to beat everyone because the shaman spell cost reduction shrine + unstable evolution is honestly just silly, I consistently had 4+ 10-drops on turn 4. I went for another run with hunter with a very subpar shrine and eventually got rekt by a druid with the mana reset upon armor gain shrine. That second run genuinely felt unbeatable, which is not a good thing. I didn't go for another run because I already had the card back from my first run, anyways. I'm not gonna say that they didn't try hard with this one, as the opposite is evident in all the emotes/possible outcomes, but I think they put too much work into things that finally don't matter as much (to me at least) while ignoring major aspects such as balance and an actual sense of accomplishment. It's no fun obtaining everything there is to get from just a single run.
Finally, I also feel like they should come up with a new main concept for every one of these PVE adventures. We had very similar PVE content in CnC/Witchwood, and after the puzzles this one kind of felt like recycled content when it comes to the actual gameplay.