Dark weasel is fine to be honest, yea it's easier for sand to farm and pretty difficult for any other village to, but every other village has item drops relatively close to their spawn points.
Rogues have Bone boss, Guren, Gafuki, and Hosts (6 weapon drops)
Mist can farm Kraken, Tanuki, or Ghosts (2 weapons, 3 cosmetics)
Sand has Dark Weasel, Big scarabs, Puppets (2 weapon drops, 2 crafted weapons)
Leaf has Rats and Rat Kage (1 weapon drop )
When it comes to imbalance of farmable content, Sand is toward the lower end of the spectrum. The new sand item just feels imbalanced right now because it's new and shiny.