Pretty good team.
I recommand Leftovers over Air Baloon on Ninetales because Ninetales must stay a lot for win the Weather War and the Air Baloon is easy break. I recommand too use a Will-O-Wisp + Protect on Ninetales for easy win the Weather War.
Ninetales @ Leftovers
Trait: Drought
EVs: 252 HP, 120 SpD, 136 Spe
Timid Nature (+Spd, -Atk)
- Will-O-Wisp
- Protect
- Flamethrower
- Hidden Power [Fighting]
Politoed and Tyranitar often come on Ninetales and take Will-O-Wisp and are easy weak with Protect. Flamethrower for the satb and HP Fighting for weak Tyranitar and Heatran.
Also, try Leftovers on Venusaur because he is your solution again the Volt-Turn.
Try Donphan over Forretress because you do'nt need Spikes and Toxic Spikes and Magnezone can be a problem, he can spin and don't break the Offensive pressure of your team.
Donphan @ Leftovers
Trait: Sturdy
EVs: 228 HP / 252 Atk / 28 Spd
Adamant Nature (+Atk, -SAtk)
- Rapid Spin
- Stone Edge
- Earthquake
- Ice Shard
Because of Heatran, you don't need SR on Donphan.
Run this spread on Sawsbuck : 104 HP / 252 Atk / 152 Spd
I hope, I help you