I think you are misrepresenting Grym a bit, he’s more of a puzzle boss, who will take large amounts of damage when the parties position him right.
BG 3 Monsters also don’t have 5e Legendary Resistance or Legendary Actions.
They showed the Psion a while back asked for feedback about a week later, then yesterday they released a version based on the feedback they got for the class. The same thing happened with a bunch of their playtest stuff.
Just because feedback can be given after a fairly short period doesn’t mean...
Video game development is much more complex than TTRPG development so 200 people makes sense there.
For the RPG I am not sure what a ton of new people can and should do outside of subbing for each other in the same roles.