Also BRD is an odd case, is technically there are two separate manifestations of it - straight out singers and performers who stick to singing in taverns, and the more combat-focused kind, which is the actual Job the player learns (also, back in 1.0 Thancred was actually frequently called one, despite definitely not using anything remotely like BRD abilities in combat).

As for the Allag clones wielding... modern Disciplines, that was something I found odd too, especially given the fact that the Disciplines as we know them now are only meant to have come into use in comparatively recent times and would not have existed in that form at Allag's height, so I'm just going to put it down to a handwave again and that it was just easier for the development team to give them existing classes and abilities rather than created 'Allag classes' simply to fit the lore.... but I guess it could also logically raise the interesting question, that the modern disciplines... aren't so modern after all, and rather than developing them in the Sixth Astral Era, all that happened is that they were restored, much like how Jobs like SCH and WHM were.

But I'm droning on here like a dysfunctional node so I'll shutup now.. bzzzzzpppp....