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I would recommend a Sitrus Berry for you Politoed to keep it alive for an extra turn or two. Also I recommend this set for Chesnaught:
Chesnaught @ Expert Belt
Ability: Bulletproof
EVs: 252 HP / 144 Atk / 4 Def / 60 SDef / 48 Spd
Adamant Nature
Hammer Arm/Taunt/Spiky Shield/Wood Hammer
With...
Your team is looking good overall but be careful when using 252/252/4 sets for your EVs. These kind of EVs are great for singles but for VGC sometimes variety is necessary to survive certain attacks or deal just enough damage. Some like your Special Tyranitar for example need to have 252 EVs it...
I would ignore the Garchomp set over9000chainz gave you and just keep your own. Your set looks better for a VGC team. Although if you want to surprise your opponent and KO any Garchomp even if you lose the speed tie you could use this set. It survives a Dragon Claw from a Life Orb Garchomp and...
Your team looks good overall but I don't see answer to Talonflame except Politoed so I recommend you run Rock Slide over Earthquake on Lucario.
You could also simply use Garchomp who can live a Brave Bird and OHKO with Rock Slide.
Choice Banded Talonflame can OHKO or have a good chance to OHKO...
How about tomorrow at about the time you sent this last message? (6:00) Also I'm a very forgetful person so can you tell me what tournament your taking about?