To be fair, we've never defeated an Unsundered without a plot device. We had literal divine intervention with Lahabrea at the Praetorium (especially after it was redone, where he outright kills the player until Hydaelyn steps in), Nidhogg's Eye at the Aetherochemical Research Facility, the overpowering Light of the Lightwardens against Hades, and Azem's crystal to summon backup for Hades and Elidibus. We also had Hraesvelgr's Eye to help fight Nidhogg.