This Resilient Leather farming guide will show you the places where I farm Resilient Leather in Dragonflight.
There is always at least 3 Ravenous Rockfang up at the marked area. There are hyperspawning mobs, so there is no downtime. There is also a quest mob there that has higher than usual HP. If you have enough damage to kill it fast, you should pull the quest mob too.
You can also kill Grazing Bruffalons, Bruffalon Calfs, Bruffalon Bulls, and Suntuft Bakars around the marked area.
The Azura Span
Look for Wildwater Ottuks and Wild Crystalspines around the marked area. They are all over the place and really easy to kill.
You can also find a bunch of Bears, Goats, and Mammmots around this same area. They all drop Resilient Leather, so kill everything. The small "Calf" mobs only drop grey items, but they will die to AoE easily, so they won't slow you down.
The Azure Herdmare drop Adamant Scales, but you might as well pull them too and AoE them down with the rest.