I don't know much about stealth in DnD 5e. I know just a little, because I watched a few episodes of Critical Role. Apparently, the assassin can still do pretty decent damage when they land a flanking attack, especially if it's a crit. The rogue of their party would do way more damage than their barbarian - again, when the conditions are favorable. That's about all I know.
5e has a mechanic called "surprise", which happens when your rogue rolls stealth and beats the enemy's passive perception score.
A surprised target can not move or take any actions during the first round of combat, and the Assassin has a skill that grants him advantage ( roll twice for attack) and an automatic crítical hit if he succeeds.
I really hope they implement this mechanic into BG3, and I'm curious to see how this could be implemented without turn based combat.
