One of the things I've always felt about the wingman, is it's supposed to be a starting pistol sidearm, like the p2020, or p45, or Mozambique. The issue is the gun surpasses most of the other guns in the game in a lot of ways, but it's just as common as any of the other pistols. I am not saying it shouldn't perhaps be the better of the pistols to choose from, but I am saying it shouldn't be a better choice then almost any other gun. Just like the other pistols it should be one of those guns that you're looking to replace quickly.
My main suggestions for fixing the gun have boiled down to this. Decrease the fire rate to match the kind of gun it is, and remove the extended mag attachment. Boom problem would be solved, don't even have to lower the guns damage, range or anything else. Still remains viable, still is strong in a lot of uses, but you can't spam shells down range because you got 12 rounds, and fire it as fast as the semi auto sniper rifle.