Teamwork, that's what team are for!

This team's Pokémon is built on each other, as they have really good synergy when played correctly. After all, teamwork is what team is for, right?

Mienshao (M) @ Life Orb
Traits: Regenerator
EVs: 252 Atk / 4 SAtk / 252 Spd
Naive Nature (+Spd, -SDef)
- Fake Out
- Hi Jump Kick
- U-turn
- Hidden Power [Ice]
Mienshao is one of the powerful Fighting type introduced in this gen. The combination of Fake Out, U-turn, Life Orb, Regenerator and great Speed is only held by Mienshao. Hi Jump Kick is obligatory STAB and extremely powerful, but I would prefer Close Combat if he learns it. HP [Ice] to break through annoying foe as Landorus, which is OHKOed after Fake Out (the offensive variant) and 2HKO Gliscor if he doesn't get two Protect in a row. Also this is the only weapon against Bulk Up Breelom.

Volcarona (M) @ Chesto Berry
Traits: Flame Body
EVs: 156 HP / 240 SAtk / 112 Spd
Modest Nature (+SAtk, -Atk)
- Quiver Dance
- Flamethrower
- Bug Buzz
- Rest
ChestoRest for Volcarona. Its EVs spread is a little different from Smogon set. I add a little speed to outspeed certain threat such as DDance Scrafty. Flamethrower is use for both damage and reliability, as its PP is high and 100 accuracy, Bug Buzz for dual STAB, but he oftens have prob again Flash Fire fire type.

Dragonite (M) @ Leftovers
Traits: MultiScale
EVs: 156 HP / 252 Atk / 100 Spd
Jolly Nature (+Spd, -SAtk)
- Dragon Dance
- Dragon Claw
- Brick Break
- Roost
Dragonite bulky Dragon Dance set. Its bulk allow him to take hit well, and reactivate Multiscale by Roost. 

Donphan (M) @ Leftovers
Traits: Sturdy
EVs: 252 HP / 4 Atk / 252 Def
Impish Nature (+Def, -SAtk)
- Earthquake
- Rapid Spin 
- Stealth Rock
- Ice Shard
Because of Volcarona, Stealth Rock has to be kept away from my team. Donphan do a great job, since he has huge def and rapid spin. If without spikes and get hit, Donphan will regain max health and regain Sturdy. Ice Shard to deal some damage before die.

Metagross @ Choice Band
Traits: Clear Body
EVs: 252 HP / 252 Atk / 4 Def
Adamant Nature (+Atk, -SAtk)
- Pursuit
- Earthquake
- Meteor Mash
- Bullet Punch
As you can see, my team has big prob with Ghost-type, and Chandelure pose a threat to both Mienshao and Volcarona. Metagross can comfortably OHKO Chandelure with Pursuit after Stealth Rock, even if it doesn't switch. Its Bullet Punch almost as hurt as Scizor's, while Meteor Mash hit any thing hard and having chance to raise his montrous Atk to terryfying level.

Latias (F) @ Light Clay
Traits: Leviate
EVs: 252 HP / 80 Def / 176 Spd
Timid Nature (+Spd, -Atk)
- Reflect
- Calm Mind
- Recover
- Dragon Pulse
Not just ghost-type, I also have prob with Fire type. Latias can tank any Fire or Water special based atk throw at it. Reflect, Calm Mind, Recover make it a mixed wall, while Dragon Pulse has good coverage and still do some amazing damage, as Calm Mind also boost her offensive stat.

My team still have some fault, though. If one key member like Donphan got KO before fulfilled its job is not good. Rate n fix my team!

For Dragonite, use Earthquake or Fire Punch over Brick Break. Fire Punch does more to Ferrothorn (at the cost of being damaged by Iron Barbs), Skarmory and Forretress, while EQ does more to Heatran.

While Donphan is a pretty decent Rapid Spinner, it shares a Water weakness with Volcarona. Starmie can cover that weakness pretty well, despite having less bulk, but that can be made up for with Recover:
-Rapid Spin
-Surf/Hydro Pump
-Thunderbolt
-Ice Beam/Recover
Nature: Timid
EVs: 4 HP/252 SAtk/252 Spe
Item: Life Orb
Ability: Natural Cure

It looks to me that you're using physically defensive CM Latias. While Latias is fast in its own right, a more defensive spread is suited for that set: 252 HP/228 Def/32 Spe with a Bold nature. Change Light Clay to Lefties; Light Clay is better suited to Dual Screeners.