[RATE MY TEAM] Weaknesses of my new VGC 2015 Team

[Kingboo421]

Hi, I know this team is fairly standard but I would just like to know all of the flaws and weaknesses it has so that i can make changes in the future!

Cresselia (F) @ Leftovers
Ability: Levitate
EVs: 252 HP / 112 Def / 44 SpA / 100 SpD
Relaxed Nature
- Trick Room
- Helping Hand
- Swagger
- Icy Wind

Landorus-Therian (M) @ Choice Scarf
Ability: Intimidate
EVs: 44 HP / 252 Atk / 212 Spe
Adamant Nature
- Earthquake
- Rock Slide
- U-turn
- Superpower

Thundurus (M) @ Sitrus Berry
Ability: Prankster
EVs: 4 Def / 252 SpA / 252 Spe
Timid Nature
- Thunderbolt
- Thunder Wave
- Taunt
- Hidden Power [Ice]

Gengar @ Gengarite
Ability: Levitate
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
- Shadow Ball
- Will-O-Wisp
- Sludge Bomb
- Substitute

Sylveon @ Choice Specs
Ability: Pixilate
EVs: 56 HP / 200 Def / 252 SpA
Modest Nature
- Hyper Voice
- Psyshock
- Moonblast
- Quick Attack

Scizor @ Lum Berry
Ability: Technician
EVs: 252 HP / 252 Atk / 4 SpD
Adamant Nature
- Protect
- Swords Dance
- Bug Bite
- Bullet Punch

Thanks!