Hey Eradicator, this is a pretty good team. There are a couple of problems it has though:
-Starmie = Basically you have no safe switch ins, since it 2HKO's and OHKO's everything you have. Your only real defense is Flygon's U-turn which is extremely unreliable for dealing with it. It also ruins your strategy by spinning fairly easily. Starmie is basically the number 1 threat to your team.
-Snorlax (and other last pokemon stat uppers) = You really can't deal with Snorlax at all, since you can basically phaze it early on easily but as the last pokemon you can't damage it at all after a Curse. Your only real hope so far as I can see would be to try and Leech Seed it with Roserade, then hax it with Jirachi.
-Heavy stall = Yeah, these could be a problem. You don't have any pokemon really capable of breaking through SkarmBliss and similar.
My suggestion is using Rotom as your Scarfer over Flygon, as it outspeeds Starmie and can therefore reliably spinblock against it, and it can Trick against both last poke stat uppers, and stall. You can keep the ScarfGon, but I would recommend changing it to either a mixed LO / Expert Belt Flygon, which can help against stall in particular; or a Gliscor. Gliscor can either run TauntToxic, which helps a lot against stall and defensive teams; or it could SR for you which would let Heatran run something like TauntRoar. Depends on your preference basically.
Finally, I would use a heavily special defensive spread on Jirachi which enables it to beat Starmie 1 v1.
Hope this helps!