by all means i heard about that the will adjust this "offstat" in the Future but to Answer the question in this thread:

IF parry is Removed, Despite the fact that one or maybe two abilites are NOT working anymore for the DRK, i would not make a big massive difference at all. You take more Damage from Auto Attacks and some other Physical abilites; Fluff Damage, some one is smacking you with a Pillow just a bit harder, that's it.

It would not make a difference at all if this "Stat" would be out of the game, the healers would probably heal you for a bit more maybe for each Auto attack that was not a "Parry", which does not make difference anyways because like the other Classes, they also have a "set Rotation" of how to heal, when to dps, etc., there are always Random Factors here and there without a doubt so you have to adjust etc., but that is how you usually Play every Class.(sort of)