Thanks man, to be fair though, the team you see up there is edited after these comments and some battle testing, it was a bit different before :)Considering this is your first attempt at making a team, I'd like to congratulate you on it before I critique it. You managed to make a semi-balance between offense and defense, without being completely weak to many of the metagame's threats. Nice job ;) But enough of being nice, it's onto the team itself...
That Mamoswine lead you have currently is nice, so I'll leave that alone. The main thing I want to look at is your Salamence. Yes, I realize you run the "superior" MixMence, and I know everyone's going to go crazy when I say this, but seriously; try the New MixMence. Outrage / Draco Meteor / Earthquake or Brick Break / Fire Blast is what I use currently, and while a lot of people are bound to go crazy using "theory" to prove its inability to deal damage, I've used it on all of my teams currently, and it deals more damage, pound for pound, than the MixMence you currently use. I realize losing Roost is a real bummer, but considering the job OF a wall-breaker is to break walls, you'll find "New MixMence" has an easier time handling things that don't die to Draco Meteor. Outrage hits Blissey harder than Brick Break anyway, though locking yourself in may seem "game-breaking". Honestly, try it out, and if you still feel like it, use the old one.
Most of the threats (Salamence, Gyarados, etc...) are pretty much covered by your defensive core, although one thing that bothers me a bit is Infernape. "But Vance, he has Vaporeon!". Yes, but he has no insurance against Swords Dance Infernape. After a Swords Dance, Close Combat OHKOs Vaporeon with Stealth Rock (even without, you get KOed 46% of the time). Blaze Kick handles Jirachi, Stone Edge takes care of Salamence, and the rest of your team is battered so badly I won't even mention it. Luckily, SD Ape is rare, but the point remains; it 6-0s you. You could consider Starmie, since it "sort of" counters Gyarados with the correct spread, although you have to make sure you outrun Infernape and can KO it with Surf. Ironically, Swords Dance Lucario isn't as big as a problem, but only because of Jirachi.
Good job for your first team. Most threats are handled are just plain beaten into submission.
I've become fully aware that I'm weak against a lot of the "rarer" threats..I got 6-0'd by an Infernape, and by a Furret that use belly drum followed by an extremespeed/return spam, and almost (barely survived) an Abipom with fakeout/Last Resort. Normally I take infernape by sending out Vaporeon and protecting for a turn to see if he's going to use Close Combat or Grass Knot, then hope to god I can outpredict him.
I also have been experimenting with Scalemance, and so far I've determined that the DD mence that was suggested just doesn't do it for my team...I have no spinner so almost always they'll have SR up and I won't have enough time to get the sweep. Not only that, but DD mence is so common almost every team has a counter. For your Mixmence though, why Outrage AND Draco Meteor? I do agree, Roost isn't really the best idea because it's not really SUPPOSED to survive, it's supposed to come in and kill things then die.