The wingman is fine, especially now after the ammo nerf. Its a high skill gun and people who complain about it are just not skilled enough to use it themselves with consistently good outcome. Sure; you can get killed very quickly if you dont know how to move when fighting a skilled player with a Wingman but what people forget in this scenario is that EXACTLY the same outcome of that fight would occur if the Wingman player used some other top tier gun. A Master/Predator with a wingman will kill an average gold player in 3-4 shots in a couple of seconds and I understand that that feels bad for the gold player but he would also had two-shot him with a PK or one-clip him with a R99 in the same time. The main "problem" is that gold players play against Predators and not the gun it selves.
I agree that it was too OP before the patch since you would have a top tier gun for all ranges with only having to allocate 2 inventory slots for ammo but the patch fixed this.
IMO, if we are gonna talk about weapons that needs a bit of nerfing then I think the PK is much mor relevant than the Wingman.