If you don't mind my asking, what Pokemon does defensive Heatran outspeed with 12 Speed EVs?
You can also consider Wish support somewhere on the team, since some of your Pokemon lack reliable recovery, like Blissey or Chansey:
EVs: 4 HP/252 Def/252 SDef
Ability: Natural Cure
Chansey: same set as above, except that Flamethrower isn't a viable option due to 35 Special Attack, the EV spread being 252 HP/252 Def/4 SDef and Eviolite as the item.
I'll post more later, but that's all I have for now.