My experience might be different, probably because I used my ranger to backstab the gyth patrol and I also surprised the beholder - but both fights were not difficult. I admit though it can be seen as exploiting the game. In any case a beholder shouldn't be taken down by a party of 4 lvl4...
I never tried to kill the Dragon because I didn't look at his level and its D&D - he shouldn't be killable at all for a group of lvl4...
Again, BG3 fails completely at giving you a sense of being in the world of Faerun. Just random encounters using known names for monsters. In BG2 the Underdark was a threatening place for place for a high level party, exactly like you knew it from the lore. Here the monsters might scare you with their ability creep, but overall it felt more like a demonstration of all kind of models they have in there with abilities adjusted to be just above your level than this being the legendary Underdark.
