They will nerf Bastion I think. I have come across a team of them too. You can set options to not allow multiple instances of the same character, but that is in custom games.
I, so far, have become pretty good with Thornbjorn (The Dwarf turret guy) and D.Va. Not too bad with Reaper and Soldier 76, but definitely smash the shit outta the place with the first two. Went on a 38 player kill streak with the Dwarf last night