EverQuest 1999 had a 1/5ths rule on hardcore players to casuals. Such that no fight in the game was so difficult to require 40 or 72 hardcore players.
That essentially made the game a great social experience. Because now there was a place in a guild for all these people. Both hardcore and casuals. Instead of being focused on challenging an exceedingly smaller number of people they took the approach of more is better and a mix of casual and hardcore players. It was probably the best time ever to be an MMORPG player and I pity those who never got to experience EverQuest during that 1999-2003 era. I say 2003 because that’s when they started instancing dungeons and the game was never the same after that.