I've found out that if you activate one of your "In-Training Whistle" while you're in mid air, you will not take any fall damage at all when you hit the ground, no matter the height.
In order to do this you must have the Stable building in your Garrison AND one of the daily quests for the Whistle (You can get these even if you've earned all the mounts by speaking to one of the NPC's in your Stable, but those will only have 3 charges).
When you are in mid air, activate any of your "In-Training Whistle" like the Snarler-In-Training Whistle and you will stop on the spot and fall straight down to the ground without taking any fall damage at all.