Dugtrio is just good in his role as Revenge Killer, and to be Honest, I don't see any problem with him, whether in NU, UU or OU, his role is always the same, of course his talent is not competitive, but the ban in NU will not change much at the tier, and then ban a Pokemon that has already been Nerf ...
for a Pokemon Overrated like him which does not stay maximun 3 turns during a game , it might be time to find out about the teambuild around and against him.