The Vampire ability Mist Form, the tooltip reads: "Dissolve into a dark mist, reducing your damage taken by 75% for as long as you maintain the channel".
It does not specify the damage source so the way it reads it should be ALL sources. However fall damage counts exactly the same as if you were not in mist form. So either this is a bug and fall damage should be reduced by 75% also or you need to change how the tooltip reads as it is very misleading.
The purpose of art is washing the dust of daily life off our souls. ~Pablo Picasso