Almost every double primary player I've matched with was mediocre at best, but usually plain terrible. Special weapons can dominate and clutch wins, double primaries just make it seem that you can't decide between what guns you want to use.

That sucks for you but you have to admit that to imply that it is an inherent loadout of a bad player is silly. What about the quick swap Bow/Handcannons strat, or the fairly popular Messenger/Shayuras loadout. You'd be hard pressed to find bad players running these loadouts. When I say bad I mean bad too, not "oh this guy had a bad game so he must be dogshit". I'm talking bout no game sense, no thumbs, and running into teammates bad.

Of course there are outliers, but you can usually guess the players ability based on their loadout. You're not always going to be correct, but most of the time it fits. If I see a player using an auto rifle, a hand cannon, and a mask for terrible stat distribution, I don't have much faith in them doing much in the game. I'm more than happy to be proven wrong, but if it quacks like a duck...