To ban Snow Cloak would mean to ban two Pokemon entirely: Frostlass and Glaceon. It's the only ability they can have. The Mammoswine Line can have it as one of the two. More Pokemon have Sand Veil then Snow Cloak with three of five families having it as their only ability.
In competitive battling no Pokemon is outright banned from play no matter how good its ability, stats, or movepool are. That isn't the point of Tier Classification.
Besides there's many ways to counter the Evasion rising / Ability.