I made this Shimmerscale farming guide to help out players who want to farm the leathers instead of buying them from the Auction House. I traveled around Zuldazar and Kul Tiras to search for places with a high density of mobs which I can kill and drop Shimmerscale. Below you will find a list of places I think are the best for farming Shimmerscale.
Vol'dun - 1
Saltspine Krolusk at the marked area respawn extremely quickly, you will never run out of them.
This place gets even better when the zone is under assault. These mobs are required to complete one of the world quests, so you can basically just run around and skin all the dead mobs that other players didn't skin.
Vol'dun - 2
Kill Scaleclaw Saurolisks around the marked area.
Kill Venomspine Saurolisks around the marked area.
Kill Shallows Saurolisks around the marked area.