Alright, my turn:
This can switch in on a Hydro Pump from any Rotom-W or Kingdra and then set up CM until it is impossible to take down. Especially the rarely seen SubCM Suicune can ruin your team due to choice items.
Too Much Choice
It is obvious that you have somehow miraculously avoided failure while using 6 choiced Pokemon. While this has givin you success, I see you falling to a Stall or Semi-Stall team with lots of entry hazards. As you must switch a lot, this can add up.
You may not like hearing this, but using a SubRoar Heatran may help more than CS Heatran. Once you set up a sub, you can remove Subbers and Set-Ups.
252 SpA, 252 Spe, 4 HP
Behind a Sub, you can dish massive damage with FB and EP, while also roar those annoying Set-Ups or Subbers.
Really can't think of much else that would prove to help more than hurt.
Well this is my attempt at a rate, so GL and somehow, your team works well. Don't forget to ask me whenever you need a team rated.