That may be true, but it won't amount to much at the end of the day. One X-Ether would net a caster pretty much one or two spells more (if that), and their overall boost in damage or healing would still be incredibly limited to that...what is it, 15 or 20 second buff? Besides, as a BLM, you should really only use an X-Ether or Hi-Elixir to set up a second or third Flare, or as a save from a bad rotation, so they gain little advantage. SCH and SMN have Aetherflow... enough said. That leaves WHM as the greatest benefactor, but that's still not much.