XY OU Pain in the Whimsi-butt

[Emris]

So I tried to build a team based around Whimsicott, but it has a few very obvious flaws, and since I'm still fairly new at this I could really use some help fixing it up. I'm willing to change any of the pokemon on this team except Whimsicott, so suggest away.

Whimsicott @ Leftovers
Ability: Prankster
EVs: 252 HP / 252 Def / 4 SpD
Bold Nature
- Leech Seed
- Substitute
- Encore
- Stun Spore

Whimsicott is a great little butt to torment people with, because like me when I first saw it, it seems like it'd be a quick KO when it fact it can just sit there vacuuming up it's opponents health.

Cloyster @ Focus Sash
Ability: Skill Link
EVs: 252 Atk / 4 SpA / 252 Spe
Jolly Nature
- Shell Smash
- Icicle Spear
- Rock Blast
- Hydro Pump

While it's great once it gets set up, managing to get Cloyster set up successfully has been a bit of a problem with this team.

Garchomp @ Rocky Helmet
Ability: Rough Skin
EVs: 252 Atk / 4 SpA / 252 Spe
Jolly Nature
- Stealth Rock Something else
- Earthquake
- Dragon Claw
- Fire Blast

While he's good at getting rid of a few troublesome pokes he can't really stand up to another dragon.

Skarmory @ Leftovers
Ability: Keen Eye
EVs: 252 HP / 252 Def / 4 SpD
Bold Nature
- Roost
- Defog
- Spikes
- Brave Bird

Skarmory completely fills it's role as a defogger...without doing much else other than picking off the occasional bug/grass type

Heatran @ Choice Scarf
Ability: Flash Fire
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
- Flamethrower
- Stone Edge
- Flash Cannon
- Overheat

Heatran is awesome, the choice scarf can be a pain, but overall I like this one except for another water weakness.

Terrakion @ Life Orb
Ability: Justified
EVs: 252 Atk / 4 SpD / 252 Spe
- Stealth Rock
- Stone Edge
- Close Combat
- Taunt

I hear everyone always talking about Terrakion and honestly he hasn't done much for me other then the occasional stone setting, and he's another water weakness.

As you can see this team needs some major help, but I'm really not sure what.
So thanks in advance for any help.​

 

[TheHoundofDoom]

Heatran should get earth power instead of flamethrower, and why have two rock setters? replace a move from either terrakion or garchomp on that. Try replacing cloyster with banded azumarill, but if you do want to keep him replace the nature to naive so sp att doesnt get hurt since your using hydro pump. Over all good team, but you will get hated from everyone you face with that whismicott so good luck on that.

 

[Emris]

I don't know why I didn't have Earth Power on there already actually, so I'll fix that, and change Garchomp's Stealth Rock to something more useful.
I know whimsicott are infuriating, I fought one and almost tossed my laptop out a window xD

 

[Ice Cold Yee Haw]

Two things, first, on your Garchomp, instead of Jolly nature use Naive/Hasty nature so that you can get a bit more damage with fire blast, second, "Something else" should be replaced with Sword Dance, +2 Dragon claw on a Garchomp can severely dent, if not faint lots of Pokemon in OU.