We actually tried falling damage in early development of Overwatch. We ran into problems with characters like Widowmaker, Reaper and Pharah. With Widowmaker, it felt strange and unintuitive to be able to grapple to high places but not be able to jump down without taking damage. We found ourselves grappling back down to lower points, which was awkward. Pharah was really odd. If you didn’t feather your jets right before touching the ground you would splat. And with Reaper, we kept teleporting to high locations with no ability to get safely down.
For awhile, we kept exempting characters from fall damage. But pretty soon, it felt arbitrary who would take fall damage and who was immune so we removed the mechanic completely.