It's either magic, or the bodies of Hydaelyn's inhabitants are just much more durable than our weak Earth bodies. Various characters in in-game cutscenes are shown to be jumping from great heights, landing on their feet, and being perfectly fine. Off the top of my head, this happens with the WoL in the level 50 NIN quest, with the Miqo'te girl in one of the Amalj'aa storyline quests, and with the Scions when we confront Arbert and his gang for the first time.