It is fairly obvious in real life that if you fall off of a cliff, you will take damage/die based off the highth of the cliff. Likewise, if you jump off of a cliff and LAND on someone's head, they are going to get hurt just as badly as you are.
While it wouldn't exactly be terribly effective it would be nice to implement the idea that if you take 10 damage on falling, and you land on an enemy, they would take 10 damage as well (or more, based off of size). This may be modified based off of tumble/featherfall. Featherfall, in my opinion, should lower the damage to the target, while tumble should lower the damage to you but not lower it to target at all (you are just landing correctly, minimilising the damage to yourself as you roll, you are still landing on the guys head).
Of course, you could take it to it's natural extreme which would start causing problems of it's own, such as spiked monsters dealing damage if you land on them (or even if you get too close during melee).