Wyvern Hide Tunic drop rate in SS?

[Shodo]

Just about everything on that loot table has a very low drop rate. When hoping for one specific item from the list (like your tunic) expect to farm there for a few days to a week or more.

That said, there is usually some one farming the fe'dars each day, so you could get lucky with a rot if you're hanging out in-zone. But they certainly aren't just laying around all the time.