AV's make stalling in Lets Go basically the only strategy in the online game. Sandslash is an amazing Physical wall and can take hits and shut down most physical attackers in the game, including Mega Aerodactyl. Maybe it doesn't immediately stop Stealth Rock, but it removes Aero and then removes Stealth Rock, which is just as good. Or you could use Alolan Sandslash, which gets Swords Dance, Ice Shard, Rapid Spin, Toxic, and a Toxic Immunity, perfect for fighting in Lets Go. If your worried about weaknesses, what do you think teammates are for? :P