Divinity: Original Sin 2

There's some semi broken build for soloing that doesn't involve prefight shit, but not sure if it won't be nerfed in the release version. Basically you get Retribution(reflect 10% of the damage you take to the enemy per point) and Necromancy(Heals for 10% of the damage you do per point) and once you scale it enough, you kinda heal most of the damage you take, making you super tanky. Also does damage indirectly, then you add whatever for damage and maybe a shield so you can use Shields Up and heal your armor.

There is also Lone Wolf(renamed One Man Army, but might be renamed back to Lone Wolf after not sure), but we haven't seen the actual release version of it, the EA one is garbage but supposedly the release one will be similar to the D:OS1. So you could 2man probably. You can't really 2man the EA that easily because CC is OP as fuck, but they're nerfing CC in the release version so that the first application of an effect gives you the minor effect(so lightning would shock you, cold would chill you etc) and then once you're in that state, another application will apply the actual effect(electrocution/freeze etc), so it shouldn't be as bad. You'd probably want some points in the shit that "heals" you after you get CCed too maybe or I don't know.

I think there's definitely going to be ways to play with less than 4, but it'll require solid planning in general, which means it might not be optimal right at launch. The issue is there's really no way to know currently because the EA is outdated shit and you can't really test much, plus the issue of late game scaling. The first game had basically 2 difficulty spikes, very early when you have shit skills and low AP and what not, and very late with the Deathknights doing high damage per hit and being immune to a bunch of CC. Most of the stuff inbetween was pretty easy regardless as long as you didn't build like non combat characters or a dual wield axes+bow with 3schools of magic to buff yourself.