I love playing as Zenyatta in 3v3s. Ana's pretty good too. Two characters I can solo badhogs with. Ana being a mechanical counter and Zenyatta apparently being unhittable if you just stay point blank and just mash A and D. That belly is bad karma. I'll sometimes pick Junkrat for our 3rd win because I can outgrease whatever they try and counter with.
Though if people are being obnoxious, like D.Va or Genji or both. Then I can bust out Zarya.
Though the best counter to a Roadhog is always being a better Roadhog. I rarely see hook>shoot>melee combos, and absolutely never see shoot>hook>shoot>melee combos. At close range, that combo can kill another Roadhog. If they have a spread out team or one that has troubles focusing, let him grab you first.