If Atomos isn't tied to Astral Flow, then it's likely to be highly magic accuracy based, and due to the fact that you cast Atomos on the mob, rather than casting atomos then using a BP on the mob, it's likely to be the SMN's Magic Acc, rather than the Avatar's. Which means another set of gear (unless you're a SMN who has an Impact set already). But let's hope not.

Atomos is either going to be really quite good, or really bad, but there's so many ways for it to be bad, it's more than likely going to be the latter.