Sickens me this hasn't got a rate or even a comment. I get that this team is very good, but still. :/ lol
Anyway, the only 'real' issue i can spot would be Dual Dance Balloon Terrakion, but it cant even set up on anything really at all.
However what i WILL recommend is that you max Salamences speed and use Naive. There is a couple of important things that are above 280 speed which your spread grants. Namely Hydreigon, Lucario (NPer might be an issue if Virizion is dead) and Haxorus but thats up to you, i feel outspeeding them is rather important. I mean unless all that attack does something important ? I also love MixMence as it beats those BS dual screen smashpassing teams and you're right its extremely underrated. :]
As for Volcarona (who is is also BS) maybe you could find room for a rock move on Tar ? It lives a boosted Bug Buzz in the sand. Better than nothing lol.
Other than that, great job really. Not many holes as said.
Oh and Shed Shell over Leftovers on Skarm imo. Mag + Drag teams are horribly common now and to lose such a vital Pokemon would be devastating for your team. Not just its defensive utility but Spikes too.