Shell Smash is quite an annoying set to fight against.
When I have the chance, I want to use Quiver Dance and Shell Smash Necturna more. The set shrang posted is really cool too, although personally I'd probably use it with more defense investment.
Lately I've been using:
Necturna @ Leftovers
EVs: 4 HP / 252 Atk / 252 Spe
- Sacred Fire (sketched)
- Horn Leech
- Stone Edge
It's a great set and can deal a lot of damage to the opposing team. Just make sure you eliminate Heatran, otherwise you won't be doing that much.
Also, what's with all the Magnezone's running around? In like 70% of my battles in the past 2 days I've seen Magnezone. It's quite annoying, especially since I use Skarmory a lot, but it's manageable.