Actually, Kyokohu does have the ability to mend the barrier as a Geomancer as it was stated his Great Grandfather kept the barrier going, but his abilities as a Geomancer was just lacking as he never was fully trained in the arts of Geomancy. That's why he turned to Astrology to supplement his understanding of a way to figure out a way to mend the barrier permanently. On later accounts of the AST storyline, it is discovered Geomancers have the ability to make a permanent barrier but it requires a forbidden technique with blood to do so.
*insert Blood for the Blood Lily joke here*
But yeah, In Foxfire Quest, it's shown that Kyokohu can heal others along with Leveva (provided you don't actually heal and spam Gravity to kill mobs first). So Geomancers are a healer class with some dps skills. He just couldn't take the Kinko on himself and heal at the same time. Really, he didn't even think of healing the kinko because he wasn't galaxy brain like Leveva. AST's kit of healing is supposed to cause a soothing and beneficial effect to the soul which is why Leveva proposed the idea to hurt and heal the kinko.
Geomancers are definitely a healer job storyline wise, and to rip that out entirely from the story would mean to change AST's level 60-70 quest lore. Though SE's been moving WHM away from the elements and making that more of a conjurer thing from what I've seen so it's possible Geomancers will replace conjurers as the Nature Healers and WHM will be the light aspected healers with Holy, Dia, Glare, Afflatus Misery, and whatever else they get in 6.0 that is more light-themed.
From a lore standpoint Geomancers will be using the elements directly versus Conjurers who commune from the elementals to activate their spells. There's still plenty of ways to make a geomancer kit unique in the sense that they use the elements to provide mitigations and shields rather than rely on regens and powerful healing like WHM. If anything, I wouldn't be surprised if Geomancers became more of a rotational-variant healer where they get a special gauge based on the elements they are currently attuned to (using one element will deplete that resource more and then their skills will lean towards the other two elements instead). Utilizing one element heavily will empower something more than another and affect the power of the land, compared to conjurers whose spells don't change as they draw power from elementals. Just some food for thought. I kinda like this idea so I'm going to throw this up on the forums.