Most people quickly discover that if you are playing PG it pays to be able to solo. If you can easily play solo you get all the xp and all the loot; therefore social advantages aside solo play is better against non elite monsters. We had a good discussion about this a few nights ago on discord. When was the last time you joined a group in the goblin dungeon or wolf cave? Note this is not the same thing as inviting someone for boss runs - but inviting them to xp with you for 30-60 minutes as you grind monsters.
Having the xp split between players means people are less likely to group. I hate this so much. The end result becomes group play = elites only.
For me and several of my friends group play is what makes the game fun.
Could we try a period where grouping does not suck up more xp as you add more players (or maybe at a reduced rate)? At the very least could we try 2 players in a group = no xp reduction?
This would be good for the game while we have limited area space for everyone to fight all the same monsters.
People would be more likely to keep playing if they can do the same content with a friend.
The obvious downside is that people would level up faster - but there is already a mechanism for that as level progress is gated by money unlocks. If you group and level up faster you get less loot so you reach the level gate slower.