The first random fight you face in the underdark shouldn't.
Enter the underdark in BG:2, walk a little bit north, be mindblasted to oblivion by three mind flayers just chillin' there. Walk a little bit east, be ambushed by a drow war party with high level clerics and wizards, just chillin' there in the middle of nowhere.
Just the first two random encounters.
That wasn't the purpose of what I wrote.
Anyway it feels a little bit natural to fight in the underdark in BG2 with "high level characters". I'm not saying we shouldn't have to at low level in BG3 nor it hasn't to be a dangerous place.
But even in the underdark you face the situation I describe. The last fight of the EA is way easier than your entrance in the underdark. Even the bulette is easier than the 2 minotors. That's not a good difficulty/challenge management to me.
No one would choose to go to the underdark if you can't deal with it. It's not like if the story was explaining something like "the underdark is the most dangerous place in faerun with the most powerfull creatures but you HAVE to go or you'll become a mindlfayer".....
