NPC gear isn't necessarily an indicator of, well, anything. Hilda wears Crafting and Maiming parts, the Ala Mhigan Resistance is a mashup of different sets, and the Xaela tribes are all over the place. NPCs aren't bound by the same limitations we are, SE just uses whatever gear they think looks good for the part.

They're also not bound to the same classes and jobs we use. Y'shtola is listed as a Sorceress, Alphinaud was an Acadamecian pre-EW, Thancred uses ninja tricks as a Gunbreaker. Zero is in the same boat. I expect that if she gets added to duty support next patch, she'll either be listed as a Reaper and just quietly ignore the job's actual abilities, or she'll be listed as her own job.