Crustle is down in RU due to there being Pokemon who can better fulfill it's roles.
Crustle is in RU's Mid B Rank.
B Rank: Reserved for Pokemon who are slightly above average in the RU metagame. These Pokemon have more notable flaws than of those above it that affects how they function in the tier. Their positive traits still outshine their negatives, but they require a bit more team support to bring out their full potential
Smogon RU Viability Thread