Your jumping to conclusions based on incomplete information. There are lots of ways to murder people (chainsaw is one of my personal favourites). Whist some of the Dark Urge gear is most useful to an assassin, others (such as Saravok's armour) are not.
I don't think that armor is exclusive to the dark urge or a dark urge specific reward. My point is about the rewards that only the dark urge can get as part of his origin story. The origin seems clearly intended to be played as a rogue assassin.