Yes, absolutely yes, albeit i may go more extreme as it really only gets superwalleed by zone, which still prob loses against kings rocknom time pog
C > C+/B-
Cloyster still being in C is absolutely criminal as it's imo a great option for HO teams. Due to its amazing defense stats setting up a Shell Smash is far from a problem most of the time and once it does most "checks" are one 41% flinch away from being in range of a +2 Icicle Spear/Rock Blast. It also greatly appreciates the decline that Rillaboom has been experiencing recently. It has some problems like how reliant it is on getting flinches but it's definetly a better option than niche mons like Salazzle, Toxtricity and Volcanion.