Forum:Argus and Valkyrie rifles: Why?

For any whose Shepards use the Argus or Valkyrie rifles: how specifically do you use them?

I've been experimenting with Vanguard, Infiltrator, and Soldier builds, and I'm finding a hard time putting them to real use. Neither of them take the best advantage of the side-benefits of the types of ammo that compute off of probabilities and shots taken (e.g. Incendiary Ammo's Explosive Burst, Cryo Ammo's chance to freeze, Disruptor Ammo's chance to stun) in the fashion that a full-auto rifle or even a multiple-pellet-launching shotgun would, so I'm assuming that those would be better used with "bonus" ammo types such as Armor-Piercing Ammo and Warp Ammo, whose damages do not compute in such fashion. In the case of the Valkyrie, I suppose an Infiltrator could use it as somewhat of a substitute for the Mattock as a "pump out many rounds as your trigger-finger allows before the cloaking expires" device, though it comes at a significant greater weight than a Mattock of comparable version.

The Argus, on the other hand, I'm having a hard time figuring out how it's supposed to be used at all. For a Vanguard's purposes, it's clearly an inferior choice compared to most any of the shotguns at Vanguardish ranges (especially since both the Vanguard's ammo powers are of "chance per projectile" nature), and for a Soldier or Infiltrator, I just see the full-auto rifles or the Mattock as being a better choice (unless I misunderstand how to use it).