Some other assorted commentary, which I assume you will find insufficient:

I've seen groups of 2-4 that didn't involve me make it "through" Hell. Some of those aren't that long ago and didn't involve super A-Ps or (as far as I know) immortals playing mortals if you want to argue that's somehow relevant.

This, to me, invalidates most of the rest of your points because you're assuming a greater necessity of collusion than has been actually shown to be necessary in practice.

I mean, we can theorycraft about what you think is necessary all day, but when people go and actually DO it with less, what is there really left to say?

I don't think you've been part of most of the groups to go; it just seems to me like, for whatever reason, you need to feel like you're the guy who's done everything and knows the most there, even though I'm convinced that's true.