The damage from destroying your Presence is part of the same action because the Special Rule says "When you destroy your Presence..." – it modifies how other actions work while they're happening. Tags: Destroy, Saved From Destruction, Action Modifiers, Damage, 25 more...
Ravage (without other effects): The Dahan are protected by the Incarna, since it was present when they were dealt Damage. But the Incarna is gone during the Dahan counterattack, so the Invaders take Damage normally.
"Draw Towards a Consuming Void," "Drought," "Poisoned Land," "Pyroclastic Flow," "Pillar of Living Flame," "Volcanic Eruption": The Incarna is destroyed at the end of the base effect, so only the threshold can successfully deal Damage or destroy anything.
"Insatiable Hunger of the Swarm": The Incarna is destroyed at the beginning of the power, so doesn't protect anything.