Yeah, not all parts. But even if it's a 1% chance, one hellscape might balance out a hundred universes where FAI wins. Pain is just too effective at creating disutility. I understand why people want to be optimistic, but I think being pessimistic in this case is more responsible.
So basically you are saying that the situation is asymmetric: the impact/magnitude of possible bad things is much much greater than the impact/magnitude of possible good things. Is this correct?