Originally Posted by Fat Rayquaza_
How about no.
Cloyster is essentially the physical version of Volcarona.
You get that Shell Smash off, you kill something with Cloyster and even sweep in not-so-rare circumstances, regardless of how "good" the opposing player is.
Sand teams in particular are horribly weak to it.
Just look at the usage of Landorus-T, Gliscor and Garchomp - all things that Cloyster easily takes advantage of. As long as they're common, Cloyster will always have an easy time setting up.
I'm not sure why you think most Fighting types easily KO back, because they don't.
Terrakion and Breloom are easily KO'd with the appropriate move before they can even move and Keldeo's Secret Sword targets its high defense stat.
That, and the fact that fighting types aren't nearly as common in OU as they were in early BW (in fact, most of them fell to UU).
If you're really scared about Fighting types then just use Chople Berry instead of White Herb (you'll take +33% damage from a SE fighting type attack, factoring the denese drop from SS, a -66% damage reduction compared to White Herb).
The problem with Cloyster is that most people run the standard cookie-cutter Shell Smash set without making changes in order to tailor it to what their team needs.
Heck, Cloyster can easily get past Keldeo, Rotom-W, Starmie and Jellicent with HP Grass if it wants to.
Having Cloyster in your team will force the opponent in keeping their Cloyster "check" alive for most of the battle, something you should take advantage of.
Notice how most of them are fighting and water types? Pair Cloyster with something like Latios or Celebi and take advantage of that.
In short, it's an effective pokemon that can easily pressure the opponent just for the threat of Shell Smash alone.
Therefore it should be, at worst, B-rank.
I had a huge post about how wrong you were and I lost it. So I'm going to sum it up quickly:
1) Cloyster is not a physical Volcarona.
a) Volcarona is not as mortally terrified of any physical attack as Cloyster is of special attacks.
b) Volcarona has usuable physical defense and it has room to invest in it via evs or nature, cloyster is shoe-horned into running speed and attack or spa to get the ohkos and speed tier it needs.
c) Volcarona can cripple a physical attacker via flame body making physical attackers even less of a threat.
d) Volcarona can actually do something without a boost. Cloyster has awful offenses without it's boost, volcarona's are actually quite nice with 135 spa and 100 spe. And cloyster's utility set isnt comparable to volcarona.
2) HP Grass isn't viable.
a) Rotom-W, Jellicent, and Starmie all take more (or equal in starmies case) damage from Rock Blast than HP Grass even if you somehow were magically running 252 SpA and 252 Atk (which is also not viable)
b) Life orb is necessary to have a chance at ohko'ing the above at +2 with rock blast, and if you are running life orb you will be at -1 def and damaged and highly susceptible to priority.
c) in Keldeo's case HP Grass can only ohko if you were running life orb and 252 SpA, which isn't viable.
d) actually run damage calcs first before spewing bs.
3) "Having Cloyster in your team will force the opponent in keeping their Cloyster "check" alive for most of the battle, something you should take advantage of.
Notice how most of them are fighting and water types? Pair Cloyster with something like Latios or Celebi and take advantage of that. "
a) Notice how most of any dragon's checks are steel types? pair them with a magnezone or gothitelle and see what happens. Your statement is true for any pokemon. If you let your check for anything die before it's served it's purpose, you're going to be in for a hard time
b) Cloyster often has multiple checks to worry about that are often included in teams naturally.
4) Breloom does minimum 95% to -1 Def cloyster with mach punch. If it is running white herb, it loses alot of damage output it needs to get past bulky waters which can at the very least put cloyster into ohko range of breloom's mach punch without the defense drop.
5) Sand teams often carry Rotom-W or Keldeo. Also is potentially checking Sand teams worth having such a hard time with sun and rain?