Maybe in the full version of the game there are more variants of that cloak.
It would make sense, since Dark Urge is a custom character and it is very difficult to design an item that has the same level of utility for all classes.
I doubt it...the Dark Urge is very clearly and obviously intended to be associated with Bhaal the god of Murder who in life was a shapeshifting assassin rogue...murder is his domain. And I absolutely believe all the rewards from following the Dark Urge are essentially boons granted by Bhaal...and they will most likely all be gear very much aligned with Bhaal's domain and style.
