My first four atma didn't take that long. When I started my fifth (Central Shroud), I thought it would go by fairly quickly. Nope. I think I've been hunting for that one for about three weeks now. The game threw me a bone, though, when I popped into Lower La Noscea, did one fate, and got that atma on the first try.

Then I went back to Central Shroud... and nothing. It's becoming frustrating and I lose a little part of my soul after ever fate that doesn't drop the atma...