It seems to be that your team relies a lot on chance... Wondering if you take Natures into account?
Meinshao - Meinshao really should work as a sweeper until it's forced to swap out (usually by a ghost type or quick flying type). Drain Punch is a VERY useful move due to its low health and huge speed and attack. It's easy to keep alive by using Drain Punch until you're forced to switch out, at which point use U-Turn to gain health back from Regenerator - foes will be hard pressed to kill it!
Hitmontop - Good Hitmontop, but do you really need 2 pure fighting types? There's nothing really wrong with its moveset, although Bulk Up could be useful to add. As an item, I'd suggest either a life orb or leftovers. :3
Shuckle - Your Shuckle would be defenseless against anything resistant to Poison or any trainer with heals... There are loads of options for using a shuckle, many of which are pretty complicated, but most tend to involve using Power Trick to get immense attack stats and then going all-out on the opponent. However if the Toxic set works for you then that's fine too ^^
Shedinja - Something I've always wanted to use, it's fascinating isn't it? As far as the little bug Pokemon goes, that seems like a pretty good move set - not so sure about Lum Berry as an item though, most of its moves have fairly good PP; something to increase speed or attack would be better used here. A lot of Pokemon in Gen V do have a rock move however, so I'd watch out there.
Excadrill - Amazing Pokemon here! So good infact that its been banned in online play. I used this as one of my main Pokemon (along with Drifblim <3) in my Black game. It's got a good move set, but two points worth considering. Instead of Earthquake, you could use Drill Run instead - Excadrill has a high enough attack stat to mean the small power difference isn't that noticeable, but the increased Crit rate from Drill Run can help in many situations - plus can you imagine it using that move? Sandstorm definitely doesn't belong on this team. With only Excadrill and Shuckle benefiting from it, you'd kill your others D: A better move could be a fighting move like Brick Break to break Light Screens/Reflects and do some good fighting damage, or even Metal Claw could be useful for the STAB and the chance of increasing attack (if you start by using it on the first couple Pokemon, the last few won't have a chance!).
For the rest of your team, I have a couple suggestions...
Gastrodon
Ability: Storm Drain
Item: Leftovers
Nature: Calm
EVs: 252 HP, 252 SpD, 4 SpA
Moves: Earth Power (but this is hard to get hold of, so Earthquake can be used instead :p), Ice Beam/Scald, Toxic, Recover
Basically this Gastrodon is extremely bulky, even Grass types will have a hard time getting through it. With the first move, Earth Power is ideal, but it can only be obtained via move tutor in Gen IV, so I'd suggest Earthquake instead for a very similar effect. For the second slot, Ice Beam is mainly for taking out the Grass Types that Gastrodon suffers against whereas Scald is for a good STAB bonus, so choose according to whether it'll be facing many grass Pokemon of not. ^^ A Physical set for Gastrodon is...
Gastrodon
Ability: Storm Drain
Item: Leftovers
Nature: Calm
EVs: 252 HP, 200 SpD, 52 Def
Moves: Curse, Waterfall, Earthquake, Recover
Basically use Curse a few times along with Recover until Gastrodon is invincible and wreak havoc. ^^ Another Pokemon to consider could be Togekiss...
Togekiss
Ability: Serene Grace
Item: Leftovers/Life Orb
Nature: Modest
EVs: Basically put most in Speed, then share the rest between Spa and Hp depending on whether you want bulk or power.
Moves: Nasty Plot, Aura Sphere, Air Slash, Roost
Just power up and heal with Nasty Plot and Roost, then wreak havoc. ^^ One more to try is...
Drifblim
Ability: Unburden
Item: Chesto Berry
Nature: Modest
EVs: 252 Def, 108 Spa, 148 Spe (non needed for SpD since Calm Mind boosts it)
Moves: Calm Mind, Shadow Ball, Thunderbolt, Rest
Basically use Calm Mind till you're powered up and probably hurt, then use Rest. You'll wake up instantly due to the Chesto Berry, then Unburden will give Drifblim a huge speed boost. With the Calm Mind and Unburden boosts, Drifblim is unstoppable. ^^
Hope this helps!
