I really don't like what Shaymin can do to this team. Registeel can take any of its hits, but Earth Power hurts like hell and Registeel can't actually do anything back bar exploding. Speaking of dead Registeel, its lack of recovery sure isnt great since it's the only thing that can stop Raikou. Your team can't really stop fire-types like Moltres very well either, and while SR eats away at them quickly, you're still in a lot of trouble when they're alive. Arcanine is great for the specs stuff, but with SR down (and it usually is) secondary attacks are likely going to beat it.
The problems with this team all come back to recovery. You really don't stand a chance against any other stall team since your team will fall into the same trap offensive teams do - the Pokemon get worn down and stalled to death. The difference is that your team doesn't pose an offensive threat, so it doesn't have a chance to blow through the opposing walls.
Another problem is that on top of no recovery outside of Softboiled Clefable and the very shaky Leech Seed, your team has trouble doing damage. Uxie, Swalot, and Registeel aren't going to hurt a thing, and only Uxie contributes passive damage in the form of SR. Tangrowth also has a powerful Power whip, but with poor accuracy and a poor attack type, it's not going to do anything either, and Clefable isnt doing any...damage. Arcanine is probably your best bet at doing damage outside of SR, but SR itself will hammer it and it will eventually fall (and really, it's not that hard to wall by Milotic or Chansey). Because of this, you're going to have a lot of trouble with bulky sweepers like Rest Shaymin, LO Milotic, and even stuff like Tauros if the user outpredicts you.
Your team is basically stall without needed elements of stall (Spikes, Toxic, recovery, etc.)
To fix these problems, I would first put in Wish support, as the previous poster suggested. A Rapid Spinner and maybe a Spin blocker would also be welcome. Leech Seed won't be enough to heal your team at all.
I would just drop stuff that isn't really doing anything. Think Swalot especially. The whole bulk of the team feels very flimsy. I would seriously consider making major changes, since a lot tears up your team right now. As I eluded to earlier, you'll want to get Spikes support and certainly Toxic poison being spread around. Clefable is the only thing that does that (and it could get something like a Chocie Band in return - not good). That way, your team will actually be able to do damage, and with Wish support, stick around long enough to let the damage really take its toll.