Wow - never replied to your question. (Don't even bother with how I'm just now realizing this.)  My apologies.  Better late than never?

I would respond in 2 ways.  First is to argue that apocalyptic eschatology is less about telling the future as literal history-to-be than it is painting a divine world view aimed at inspiring current change of heart in line with God's desires for God's people.  (Because we imagine such-and-such to be the case you should act now in such a way that your life is in line with this end result.)

Secondly, its probably very important to note that neither the sheep nor the goats are aware of their wrong/right living.  The text itself resists judgement from any but the Human One, even self-judgment.