Just tried out my team:
Cloyster @ Focus Sash
Latios @ Life Orb
Metagross @ Steel Gem
Used Surf instead of Grass Knot, and Lum Berry and Hammer Arm instead of Steel Gem and Bullet Punch. My streaks aren't good yet. I mainly lost to misplays and hax (go to hell Quick Claw Donphan). This has demonstrated that there are many things that can beat Latios and Metagross, as they have come out after Cloyster died and destroyed me. The worst I've faced so far is Gengar. Metagross can't really switch in as it gets hit hard on its weaker special defence stat, while Latios can only win if it wins the speed tie.
I've realised that I went the wrong way about picking teammates for Cloyster. I originally picked Latios and Metagross because they covered Cloyster's (and each others) weaknesses, but in hindsight this is stupid logic. Because of Focus Sash and Shell Smash, Cloyster doesn't really care about its weaknesses (other than the fact that they make it hard to get more than 1 Shell Smash).
So instead, I should be covering the things that Cloyster DOES mind. From the brief amount of playing time with Cloyster, I've identified three main threats that other people interested in playing with Cloyster might like to know (excluding hax, of course):
- Status - poison isn't so bad as it just means that I can only get one boost (often this is enough), but paralysis, burn and sleep (and freeze) ruin me.
- Water types - they resist both STABs and many can survive a 2+ Rock Blast (and it can miss the ones that can kill like Starmie).
- Steel types - they resist my strongest attacks and many can survive a 2+ Surf, allowing them to prevent a sweep.
Milotic is the worst lead to face as even at 4+ attack, it can shrug off Rock Blast and kill me with its special attacks or confuse/poison me.
So with all this in mind, I will be picking teammates that can deal with these things way better than Latios and Metagross. Not sure what I'll use, though they will likely both use Substitute. Maybe Garchomp and Ferrothorn...