The pain vessels were never revived from Edo Tensei. Rather I believe the ability to create the 6 paths of pain come from the rinnegan and the black chakra rods that the pains have on their bodies. I understand that Obito's 6 paths of pain are Edo Tensei Jinchuuriki, however I am fairly certain that Nagato did not know how to cast Edo Tensei, nor did he know anyone who could use Edo Tensei.