Path of Exile actively punishes late/end-game players wanting to play with friends, and every new league seems to make it worse.
Diablo IV is too new to tell, but it does seem to reward multiplayer.
I'm hoping that PoE2 addresses the issues that hurt its multiplayer prospects beyond levelling and early maps (mid-game). It doesn't matter who you talk to or which streamers you follow in PoE, they all have issues with multiplayer because there are so many of them. My personal top three issues with PoE multiplayer are:
- Map portals (the number of total deaths allowed per map) are not increased with player count, despite the increase to the amount of damage enemies do per hit, the additional time enemies are alive for (because even the best groups aren't perfect at focusing on the same target), and the decrease to the "safe" area in any given boss arena because persistent player-targeted floor hazards like fire and acid pools will cover much more of the arena unless all players always stand perfectly on top of each other.
- Endgame/League/Atlas quest progress; Map sustain has been an issue at some point in several leagues, and only the player opening the map gets map drops. Also, while many quest/objective drops drop for all players if those players are at the exact same point in the quest, the chances of everyone being at exactly the same point in the quest chain is very very low, so nine times out of ten, the guest players in a map will have to redo it to progress their own endgame objectives.
- Screen spam and lag; Not only is playing in a map with 5 other people far far more likely to result in your death, it's also often impossible to see what the heck is going on with 6 players worth of skills spam blinding you, covering up any hazards on the floor, and making even the highest-spec PC lag out and become nearly unplayable.
That's why I stopped playing PoE a year ago, and as far as I can tell, Diablo IV has none of those issues. Enemies don't seem to be massively more lethal (yet) when there are four of you fighting them at once, having friends with you increases your chance to survive thanks to combat resurrection, and performance seems good so far with no major hitches from netcode being overwhelmed, and the skill effects of other players are translucent and do not obstruct your view of the enemies you're fighting or the hazards you're attempting to avoid.