Current State of End-Game Contents - A Blog Post from A Japanese Player

[Edli]

but for example stuff that has an "echo" buff should be steamrolled.

That's a whole other discussion though. I guess you can tweak mechanics for old content. Still a lot of what you said before can be achieved on echo buffed content. You can clear it with only 7 or 6 players so yeah you can carry two other players. There have been twintania and titan wins with even 4 players.