Ultimately, I think that the Atma quest was designed as a "casual" way to get nice items. As in, you don't have to spam multi-hour-long raiding sessions (with hours of maintenance behind them!) to get shiny gear, and can instead pile up those 1-hour-per-week stints in order to eventually get something.

Problem is, it seems as though the RNG is far too severe, and it appears as though people are getting jack squat despite hard-grinding the fates for hours on end. That's an issue. I'd suggest multiplying the drop rate by X times, and then requiring X "Atma Shards" in order to piece together the full Atma. It's still RNG and it's still grinding, but it should help reduce the raw RNG dickery at play here. Alternatively, you can have the certainty of "Atma Shards" dropping every time, but the quantity per FATE is randomized to ~1-4 instead of a flat value (because Skinner Box).