Even with the astro quests, the Geomancers aren't healers. They use CNJ animation but only for the offensive elements, and even within the game lore there is no Geomancy healing. Just vanquishing evil spirits and purifying the land. They call it the foil to Astrologian, painting the contrast of heavenly and earthly energies, but as far as I'm aware there is actually nothing in the game where Geo heals. In the lore they're known for being powerful casters doing things like bringing down airships. I'm not saying its impossible it just does seem to fit when you look at the job as a whole within and without the game's lore.