From my playing experience, I've noticed that the only teams of mine that had any reasonable success used a Bronzor/Gligar/Clamperl core.
Bronzor @ Oran Berry
Ability: Levitate
EVs: 220 HP/8 Atk/232 Def/12 Spd/8 SAtk
Sassy nature (+SDef, -Spd)
- Earthquake
- Hidden Power [Ice]
- Stealth Rock
-...