Before I respond, I need to ask a question: Are you arguing that Sidious being able to casually drain the populace of Byss gradually is more impressive than Vitiate consuming Ziost, its inhabitants, the fauna, etc, or that Vitiate choosing to kill the inhabitants of New Adasta conventionally before wholly consuming their spirits is proof that he can't gradually leech off of their energies without killing them? Because it sounds like you're trying to argue the latter, but you contradict that by stating that the death field is an expression of force drain, meaning that Tenebrae is able to kill and consume the entire planet with drain/without resorting to conventional weaponry first.