Thanks a lot for the good feedback, it’s amazing to hear that somebody went into depth to come up with such details!
The thing about not being able to deal enough damage because of how ingredients are distributed is definitely true. I briefly went over it here, how it may also be a good thing to not always have damage available, since if you do it becomes pretty straight-forward to just sit still and kill everything.
I definitely really like your idea about adding a boss/key system. I am only afraid that making it mandatory could soft-lock players since ingredients are finite. I could remove rare recipe drops from chests and make them a guaranteed boss drop to incentivize killing them, but then that would have to stop at level 15. It could also be that 8 ingredients (with 512 combinations) is too much when you can only make 15 potions, could be that the main issues would be automatically fixed if I reduce that, allowing the player to just craft more things at any given time.