I also tend to try & long rest as little as possible - so I do enter some of the fights with quite a few buffs & spells not available.
Hadn’t thought to go back & raise the Minotaurs...some of these things is just how I play - raising strong enemies & using them to steamroll content just feels off to me - but that’s just me.
I think party composition definitely impacts your game but again that’s what makes this game so good. The more I play it the more I learn & the more I enjoy it.

I agree the under dark should be hard - it’s that balance of challenge and reward - I think is pretty much spot on at present - having said that lord only knows how I’m going to kill the bulette 😉