Sammael is dead. PoD contains a very definite piece of evidence mentioned casually in conversation between Alanna and Cadsuane: 'He was injured, and then not, but I don't think a sister Healed him.' This proves conclusively that Sammael is dead. Reading the passage, it is obvious that due to the time frame, Alanna is referring to the wounds Rand received fighting Sammael (burning thread through the heel, etc), and that they disappeared without being healed by a sister or through natural healing. The only other way that this could have happened is if Rand balefired Sammael such that his wounds never occured, and Alanna merely remembers them. Therefore RJ was clearing up the matter of Sammael's death, giving us proof of it.