Thanks for the tip, i'm definetly going to use Gastrodon instead of Swampert and I might consider switching out Garchomp for a Scizor. I might not though, considering it could just outspeed, HP Fire, and take out Scizor. My Gastrodon's EV's and stats will be:
Gastrodon @ Leftovers
Trait: Calm Ability: Storm Drain
EV's: 252 HP, 252 SpD, 4 SpA
Ice Beam(For taking out Latias)
Thanks for the tip. Ill see what other people would suggest.