Epicurus doesn't assume anything here. If the 'higher goal' involved human suffering, then why would you condone that and worship the originator of suffering?
If your god would be a real person, you would not just accept 'oh, but I have a plan!'
I can't really empathize with someone who sees no value in suffering. Suffering is not the ultimate evil, and pleasure is not the ultimate good. Go read some Cicero. He tears Epicurus a new one in much better language than I can muster.