Abilities and items would greatly be appreciated here.
Combusken simply isn't viable in OU because it's frail, even with Eviolite. With Blaziken in Ubers once again, the only viable Gen III Baton Passers are Ninjask and Gorebyss:
Ninjask:
-Substitute
-Baton Pass
-Protect
-Swords Dance/Toxic
Nature: Bold
EVs: 248 HP/236 Def/24 Spe
Item: Leftovers/Mental Herb
Ability: Speed Boost
Gorebyss:
-Shell Smash
-Surf
-Substitute/Ice Beam
-Baton Pass
Nature: Calm
EVs: 252 HP/24 SDef/232 Spe
Item: White Herb
Mega Gardevoir should use Hyper Voice over Moonblast, as it becomes a Fairy move under Pixilate. Pixilate doesn't affect moves that are already Fairy type. If you want to use Moonblast, use regular Gardevoir.
Extreme Speed is what sets Dragonite apart from other Dragon Dance users because it gives it a revenge killing tool for whatever it can't outspeed:
-Dragon Dance
-Dragon Claw/Outrage
-Extreme Speed
-Earthquake/Fire Punch/Thunder Punch
Nature: Adamant
EVs: 4 HP/252 Atk/252 Spe
Item: Lum Berry/Leftovers/Weakness Policy
Ability: Multiscale
Skarmory's ability should be Sturdy and its nature should be Careful if it's using a specially defensive spread.
Why are you even using Whiscash? It's badly outclassed by other Water Pokemon, even by Swampert. Heck, even Crawdaunt is better:
Swampert:
-Waterfall
-Earthquake
-Superpower/Stone Edge
-Ice Punch/Stone Edge
Nature: Adamant
EVs: 172 HP/252 Atk/84 Spe
Item: Choice Band
Ability: Torrent
or
-Stealth Rock
-Earthquake
-Scald/Waterfall
-Toxic/Roar
Nature: Relaxed/Impish
EVs: 240 HP/16 Atk/252 Def
Item: Leftovers
Ability: Torrent
or
-Waterfall
-Earthquake
-Ice Punch
-Stealth Rock/Roar/Toxic
Nature: Adamant
EVs: 240 HP/252 Atk/16 Def
Item: Leftovers
Ability: Torrent
Crawdaunt:
-Crab Hammer
-Knock Off
-Aqua Jet
-Crunch
Nature: Adamant
EVs: 4 HP/252 Atk/252 Spe
Item: Choice Band
Ability: Adaptability
or
-Swords Dance
-Aqua Jet
-Knock Off
-Crab Hammer
Nature: Adamant
EVs: 4 HP/252 Atk/252 Spe
Item: Life Orb/Mystic Water/Splash Plate
Ability: Adaptability
Meteor Mash is Metagross' strongest STAB move, even though it got nerfed slightly. Use it:
-Meteor Mash
-Earthquake
-Bullet Punch/Zen Headbutt
-Pursuit/Ice Punch/Thunder Punch
Nature: Adamant
EVs: 252 HP/252 Atk/4 SDef
Item: Assault Vest
Ability: Clear Body