Four major things:
-1. The setup.
Unless this is for triple battles you have miscalculated how many turns you need by +2 due to switching Shuckle/Banette and not being able to move the same turn. This means you need approximately 9 turns to be all set up. In 9 turns any decent player will have found a way stop this, such as with Taunt, phasing moves or sheer power. The chance of this plan working isn't that low, but the chance of getting it up is slim to none.
-2. 4 Pokemon strategy.
At the moment you are using 4 Pokemon to pull this strategy of, two of which are death fodder. This means you will have 4 or fewer Pokemon to work with once the strategy is up. This means the opponent can overwhelm you with pure numbers, or you lacking the appropriate Pokemon to deal with his/her Pokemon.
-3. No offense.
At the moment you have no way of hitting back with this strategy. Once you are set up you are merely able to sit there, soaking up damage and waiting for the opponent to kill himself. Few opponents are so cooperative, meaning that this strategy have very little point.
-4. Minor issues.
Lastly this team have several minor issues, primarily in the moves so I will be quick here:
Refresh can't be used whilst sleeping, making it pointless and making Snorlax take three turns to heal.
Despite a Choice Scarf, Gourgeist is still in the red when it comes to bing outspeed.
Trick-Or-Treat only change the weaknesses, switching Fighting for Ghost, and despite it gaining two immunities it gains no resistances. Overall it's just pointless.
The other Pokemon have no moves. This will of course not be the case in an actual battle but I can only work with what you have given me, and that is really lacklustre at the moment.
Quick Claw is quite frankly a bad item, plain and simple, 9 out of 10 times a Choice Scarf would be better.
Shuckle shouldn't even try to be fast, he's a wall, not a speed freak.
So in short you have a strategy that is difficult to pull of, serve no purpose and takes up a majority of the team, riddled with minor flaws. If you really want to use Curselax I'd recommend just using it, and switching the other three out for something more viable. At this point this strategy is to much work to be usable and not nearly enough gain to pay of.