http://www.belloflostsouls.net/2014/10/40k-rules-conundrum-new-dark-eldar-meta.html
TL'DR:
The rules for DSing mae it a very good arguement that DSing units are counted as a Movement. B.c DS'ing is a movement, then you look at the Movement rules for Skimmers, Skimmer rules say you cant move the model over other units and move it within 1", so you cant mishap against units.
So you DS 4-5 raiders in FRONT of other players UNITS and if the DS scatters onto them, you place it 1" away instead (There fore you DONT Mishap)
From my own research in the BRB, I believe and will argue that the DSing unit DOESNT count as having been "Moved" or "Moving" until it has ben placed (I may be wrong tho).
BRB pg. 162: Deep Striking units may not move any further, other than to disembark from a Deep Striking Transport Vehicle if they are in one.
They count as having moved in the previous movement phase, and vehicles count as having moved at Combat Speed.
BRB pg. 162: If any of the models in a Deep Striking unit cannot be deployed.... something has gone wrong (consult the Mishap chart).
BRB pg 89: If a skimmer is forced to end it's move over friendly of enemy models, move the skimmer the minimum distance so that no models are left underneath it.