What you have here is a single team used in VGC17, and that's not good. First of all:
Clefairy-> in this meta clefairy needs a bit more in special defense and moves like calm mind and aromatherapy make no sense, i suggest:
Clefairy @ Eviolite
Ability: Friend Guard
Level: 50
EVs: 228 HP / 172 Def / 108 SpD
Calm Nature
IVs: 0 Atk
- Follow Me
- Ice Beam
- Encore
- Protect
ice beam for garchomps, encore to encore porygon2 if it uses trick room
for cloyster i don't have much to say but i prefer to have protect on a pokemon with focus sash so i would go with:
Cloyster @ Focus Sash
Ability: Skill Link
Level: 50
EVs: 252 Atk / 4 Def / 252 Spe
Adamant Nature
- Shell Smash
- Icicle Spear
- Rock Blast
- Protect
i like wishiwashi but, as always, use protect on every pokemon unless there is better moves that you can not get rid off and surf hit your partner so use scald (burn chance is a good thing):
Wishiwashi-School @ Wiki Berry
Ability: Schooling
Level: 50
EVs: 244 HP / 252 SpA / 12 SpD
Modest Nature
- Scald
- Ice Beam
- Hidden Power [Grass]
- Protect
Arcanine is ok, same thing, protect over morning sun, arca doesn't need recovery
That pheromosa set is bad, roost on a pokemon so fragile is nonsense, bug buzz isn't a good move, in this metagame bug isn't a very good offensive typing and i prefer poisinium-z for a surprise kill on all tapus with poison jab or fightinium-z for easy KO on many pokemon, especially on porygon2 and i'll go for adamant because even adamant pheromosa will be faster that koko and aerodactyl, the fastest pokemon after pheromosa
Pheromosa @ Fightinium-Z
Ability: Beast Boost
Level: 50
EVs: 252 Atk / 4 SpA / 252 Spe
Adamant Nature
- Poison Jab
- High Jump Kick
- Protect
- U-turn
On the last pokemon is not easy, there aren't many follow me users, the best thing i can think of is a fake out user like salazzle but is very frail, Alolan persian is a good choice, so it is Alolan raichu to use the opposing electric or psychic terrain or togedemaru, it can redirect electric type move that threatens your cloyster, it has a fast encore, a simple set can be:
Togedemaru @ Air Balloon
Ability: Lightingrod
Level: 50
EVs: 252 Atk / 4 PS / 252 Spe
Jolly Nature
- Zing Zap
- Nuzzle
- Fake Out
- Encore
Hope i helped.