I think small groups of characters could add a lot to the game, as content gets added and there are 100+ spells and traps to pick from it should be simple to equip a small group with different yet ballanced equipment loadouts. This could be interesting with restricted inventory slots, making you build up a group that can counter all of the different element resistances and terrain features. This would, in my opinion, give the player characters some life, each one bringing unique skills to the group instead of a one man army who can do all.
I also think that it suit's the game so much, its a harsh world out there, robots and magic and wild savage animals, it takes more to change this world than what can be achieved by one person at a time, and I dont like he Chosen One vibe at the moment, to me it doesnt suit a game with permadeath, this world will kill scores of young brave people, it doesnt need them to line up in single file and each be declared the one and only hope before nabbing them brutaly
Also I think groups fit in with the world since, well, its going to be multiplayer so there will be groups of people running around anyway.