My set for barbaracle:
Razor shell- stab, tough claws boost, lowers def
Brick break- tough claws boost, breaks screens, coverage
Shadow claw- tough claws boost, high crit hit rate, coverage
Shell smash- instant sweeper
Likely tier for him is RU/UU because of his weaknesses to common move types (ground, fighting, grass). Definitely not on the same level as cloyster as a shell smasher
Ghost-fighting is perfect neutral coverage. Cross chop is unreliable, as is stone edge. put him in the sand if you want to bulk up his spdef and he can become a wrecking ball (which would work well with bulk up and a shell bell if you could pull a few off without getting slaughtered). Put him in the rain to wreck ground types and fire types, but swift swimmers with grass moves (notably hpgrass) will give you trouble. Toxicroak cannot wall this set and will likely fall to a smash boosted shadow claw. He will perform terribly in the sun because of chlorophyll abusers and solarbeam from fire types.
By the way, I would not recommend night slash over shadow claw because of justified switch ins and because toxicroak will resist your full moveset