The Atma drop-rate is self-defeating in a way.

As have said, I've had very little luck with having any drop; since OC launched I've managed to obtain all of five Demiatma's and even then only three colours.
I'm not going to explore the mathematics of it all but I strongly suspect that, with the drop-rate being as appalling as it is, despite needing another four Cruiser Holosabers I'll be able to obtain another Historia weapon (from the M8 weekly) before I get anywhere near obtaining an OC relic weapon. Sorry, but that's just pathetic.