A full health tank merc will die when not in combat when gating to Plane of Knowledge from Meldrath's Majestic Mansion. Steps: Access Meldrath's Majestic Mansion with a merc Cast Gate to PoK while not in combat and with merc at full health Notice when arrive in PoK that merc is now dead.
I gave this a like - does happen but not often and I have not bothered to note the zones but not just Meldrath cause I haven't been there in a long time