Ok I'll show you what I've changed then I will explain my reasoning.
Skarmory (F) @ Leftovers
EVs: 252 HP / 216 Def / 40 Spd
Impish Nature (+Def, -SAtk)
- Stealth Rock
- Brave Bird
Tentacruel (M) @ Black Sludge
Trait: Rain Dish
EVs: 252 HP / 232 Def / 4 SDef / 20 Spd
Bold Nature (+Def, -Atk)
- Rapid Spin
- Ice Beam
- Toxic Spikes
Infernape (F) @ Life Orb
Trait: Iron Fist
EVs: 252 Atk / 4 SAtk / 252 Spd
Hasty Nature (+Spd, -Def)
- Close Combat
- Mach Punch
Haxorus (F) @ Choice Scarf Band
Trait: Mold Breaker
EVs: 4 HP / 252 Atk / 252 Spd
Jolly Nature (+Spd, -SAtk)
- Dragon Claw
Genesect @ Choice Scarf
EVs: 208 SAtk / 48 SDef / 252 Spd
Rash Nature (+SAtk, -SDef)
- Ice Beam
Blissey (F) @ Leftovers
Trait: Natural Cure
EVs: 4 HP / 252 Def / 252 SDef
Calm Nature (+SDef, -Atk)
- Seismic Toss
- Thunder Wave
You are putting to much pressure on getting the hazards up when really Skarm doesnt need to.
If you slap on Whirlwind it allows you to phaze out sub abusers and Pokemon setting up.
It also gives you an advantage in late game when i clean sweep is easy thanks to rocks.
You could use Spikes instead of rocks and then use Stealth Rocks on Blissey.
That way you will hvae all hazards and you can annoy the opponent.
Though using Spikes instead would mean using Softboiled over Wish on Blissey.
Which also means you loose Wish support though on the bright side only two pokemon can really abuse Blisseys pass as your team is a bit on the frail side.
Its Def may be sky high but its Sdef is not exactly on par hitting only 45 allowing you to take allot of damage from rain teams.
Tentacruel is OU for the very purpose your using Cloyster for.
The only differance is typing and more balanced Def.
Its Poison typing is good for blocking toxic users when you don't have Skarm.
Black Sludge puts off trick users.
Overall Tentacruel is the better option.
I guess you could keep your set but this set you may find more usefull.
Personally i don't like this Pokemon in Ou and i would probbaly replace him but that would be for another dragon which would make your ice weakness a bigger problem.
But either way this Pokemons speed sucks.
97 Means its outclassed by so many pokemon thanks to its pitfull defenses allowing any pokemon to come in and ice beam it.
Further more pokemon Like Heatran on a balloon or even worse Ferrothorn cause big trouble for this set.
Thats why you want to be hitting as hard as possible when possible.
So a scarf seems a mature choice but then again its atk is just to tempting to give it a choice band.
Witrh a Band and the coverage it has it will be hitting like a truck though you will be missing out on speed.
This Pokemon is used on almost all team mainly because of the set i have given.
99 speed also sucks in Ou and a drive is not the way to combat that.
Choice Scarf allows you to out speed praticly all non scarfed pokemon and Gnesect can hit very hard thanks to almost perfect coverage and Download.
Just try this set and you will know what i mean.
Thunder Wave is here over Toxic as you have Toxic Spikes already but it alows you to screw with the opponents team and really let your pokemon such as Haxorus shine.
Afterall you dont wont to be moving after a Cband Haxorus.
Though Toxic is still very viable i just prefer T-Wave.
Obviously you could put Srocks and Softboiled in instead of Pretect and Wish bu thats only if you want all 3 hazards.
I prefer Seismic Toss over Flamethrower as Flamethrower from Blissey is like a 4 hitko on Ferrothorn :D
By then you would be seeded and attacked.
Seismic Toss always does 100 damage which is nice in late game.
Overall nice team looks like it would work pretty good in battle but even better with the suggestiosn I've given.