This is a cool team, and your success on the ladder with it just proves that all Choice teams can work in this metagame. However, I think that as a Choiced team, you be be extremely weak to entry hazards, Deoxys-D offense teams, Ferrothorn Rain teams (since it completly walls Vaporeon as well as Latias) Skarmory (which walls Gliscor and can set up on choiced Earthquakes etc.) stuff like Heatran and Tyranitar will also find a ton of opportunities to set up their Rocks on your team, and fairly early. Since your team carries 6 choiced Pokemon, you'll litteraly going to be switching all the time, constantly taking additional damage from SR+Spikes, which is more than a realistic scenario. This means that you lose 25% right off the bat on half your Pokemon upon swithing in, and you also get Jirachi losing ~19% and Gliscor/Latias, who lose 12%. Your team will then be more than prone to be swept by set uppers such as DD Dragonite who can take advantage of Mamoswine being weakened and simply KO it with ExtremeSpeed, and this is simply an example, there are many others. You will also have issues taking resisted hits, and this is pretty much how an offensive team works, you want to switch into resisted attacks to wreck stuff. Still, with all the hard hitters in the metagame who will hit you for ~40% with a resisted hit, losing 25% right away might very well reduce the effectiveness of your checks. I think that using a Choice Specs Starmie instead of Vaporeon would be the best solution here, as while Starmie is much less of an underrated Choice Specs Pokemon, it learns Rapid Spin, allowing you to keep your team alive and remove all entry hazard from the field. With Sandstorm gaining back it's former popularity, it will happen often that entry hazard damage will not be the only residual damage you're going to be dealing with and you really want to minimize it.
Honestly, I'd give Fire Blast a try over Overheat on Heatran, as the power loss isn't that big and you can actually spam it. But yeah that doesn't change that much.
I like your team's concept n_n. Here's the set you should use:
@ Choice Specs
EVs: 252 SpA / 4 SpD / 252 Spe