I'm Reaper master. You may only want to choose him in Chateau Deathmatch cuz he and that map = always win (top4) but I always ended in top 1 or top 2 lol
I don't think I've ever seen Ana or Zen in deathmatch but I don't play it that often. I tend to play Sym if I ever play it and just sort of set myself up on a corner or a choke point. That or Torb and just keep moving the turret around to various high up vantage points