Rate my Gen 8 OU Stall team

Question

https://pokepast.es/e8a52a0d239819b1 Please tell me how to improve and preferably in the form of a pokepaste.

Ferrothorn @ Leftovers
Ability: Iron Barbs
EVs: 252 HP / 4 Atk / 252 Def
Relaxed Nature
IVs: 0 Spe
- Gyro Ball
- Leech Seed
- Spikes
- Stealth Rock

Toxapex @ Black Sludge
Ability: Regenerator
EVs: 252 HP / 252 Def / 4 SpD
Bold Nature
IVs: 0 Atk
- Toxic
- Scald
- Toxic Spikes
- Recover

Quagsire @ Leftovers
Ability: Unaware
EVs: 252 HP / 4 Atk / 252 Def
Relaxed Nature
- Scald
- Earthquake
- Toxic
- Recover

Clefable @ Leftovers
Ability: Magic Guard
EVs: 252 HP / 4 SpA / 252 SpD
Calm Nature
IVs: 0 Atk
- Wish
- Teleport
- Moonblast
- Protect

Blissey (F) @ Leftovers
Ability: Natural Cure
EVs: 252 HP / 4 Atk / 252 SpD
Calm Nature
- Seismic Toss
- Toxic
- Heal Bell
- Soft-Boiled

Corviknight @ Rocky Helmet
Ability: Pressure
EVs: 248 HP / 252 Def / 8 SpD
Impish Nature
- Body Press
- U-turn
- Defog
- Roost

Comments

TBH its pretty good but most stall teams I see nowadays have this type of shuckle set
Shuckle  
Ability: Contrary  
EVs: 248 HP / 8 SpA / 252 Spe  
Timid Nature  
IVs: 0 Atk  
- Shell Smash  
- Toxic  
- Infestation  
- Protect