[Neus]

You can trigger the elemental damage by having yourself and the target be airborne. To get the damage bonus, you need to be in Reaver stance and have Bonus Bloodshed. The elemental impact only changes the damage types to a single element - the bonus damage is still calculated from all four.

Please double check and make sure you are in Reaver stance and have Bonus Bloodshed, otherwise you won't get any damage difference.