Lol, pages of discussion about how drop rates and RNG work...

The issue with atma farming is that it isn't fun. I had 1 piece take me near 10 hrs of farming before it dropped. Grinding for that long against low lvl content, without making any progress, is not fun. These fates aren't risky or challenging, don't offer valuable rewards (save atma), and you have no idea what the value of your time spent will be.

The books to do the animus upgrade are much better, imo. It will likely take me longer than the initial upgrade to atma, but I can see my progress and aside from waiting for the occasional fate, have an idea about the amount of benefit I receive for the time I invest.