Actually, they became inefficient around the time ToAU was released, with it's mobs that had considerably lower hp then their exp would suggest, and with some mobs being great to exp on, but horrible to cast on (colibri). I mean come on, name one VT mob from the old areas that you could easily solo chain 3-4 on with a job like BLU, netting ~300+ exp per kill, w/o the ring. (speaking of course of the paper thin imps) The whole reason most parties needed SC's in the old areas was because the fact that blm was needed to drop the mobs hp quickly (dhamels in Bibiki Bay for example). In the new areas, blms would be overkill, the mob dieing before we even got off one spell.