Pretty much all the new vanguard guns are garbage when compared to the pre-dlc versions. The Devil You Don't is pretty bad, even the RNG versions of it. The Vanguard one... Man, it's one of the worse handcannons I've seen yet. 5 Bullets in the mag, low impact and low range makes some rare hand cannons a lot better than this one. If you don't mind losing your exotic slot, Hawkmoon or Thorn would be the better choice for a Hand Cannon nowadays (PVE). The Last Word is a beast for PVP, and is decent for PVE. If you want to keep your exotic slot, the hand cannon from the crucible (something 1969, I don't remember) is actually pretty decent. The Chance from FWC now has field scout, so is actually a decent choice too. What I would really like to get is either a decent Venation III or Red Hand IX, but those are completely random drops.