I've been testing the game for several hours, doing 3 runs from scratch, and this is my feedback.
1) The game becomes impossible after dungeon number 12 or 14 depending on your gear, but basically, equipment and stats doesn't improve from purple, so the stats are very limited and the difficulty keeps increasing.
The only thing I feel I have left to do is level up until I can overscale the creatures, which isn't motivating.
2) There's a bug where if your stash is full, the last slot isn't used, but if you move an item there, it's destroyed.
I'm going to assume that people who were able to complete the game at level 11 did so on an earlier version, because even with a level 30 party, full purple gear, with 9 companions I can't get past level 14 (and that's even though I tried to avoid fights as much as possible).
Despite everything, the game has a lot of potential, it just needs some fine-tuning.