Last I checked there is no difference between the perks on any Dreg's Promise so it can't have "the right weapon perks." The only armor perks that would affect it would be special weapon loader and the one that lets you carry more ammo for special weapons because there are no sidearm specific armor perks. The main problem with Dreg's Promise is that it's shots have travel time. It also has a weird hitbox with its shots that causes them not to register sometimes. Literally any other exotic secondary kills enemies faster and more reliably than Dreg's Promise. (with the exception of Queenbreaker's Bow) Also, the maximum magazine size of Dreg's Promise is 21. It fires three shots with one trigger pull so in reality it's 7 shots per magazine. Vestian Dynasty's is 15. Vestian Dynasty also does not take up an exotic slot allowing for a Exotic Primary of Heavy to be used. In regards to PvP the meta right now is dominated by exotic Primaries which is why you almost never see this gun being used. The meta also gimps Sidearms in general. They're meant to be used for fast damage against a foe that's rushing you. For example a shotgunner sprinting towards you. However, with the way shotguns are now they can get off a shot that kills you from a ridiculous range. Sidearms do t have the best range and as a result of that along with the travel time for shots you usually end up dead before being able to finish off the opponent. I honestly love the idea of the Sidearm class by right now the only Exotic sidearm is just not viable in that many situations. Fun to use but not viable.