Actually, CNJ as originally designed at 1.0's launch was less a healer and more an elemental caster class - they had spells of all elements, including fire, lightning and ice. It was only when Jobs were added that the class was completely redesigned to allow them to concentrate more on healing so as to lead into WHM, and a lot of it's elemental spells were added to THM. Sure it might not be as potent as THM/BLM, but CNJ can definitely still function as an effective offensive mage anyway (it's what Cleric Stance is meant for after all.

GEO (Geomancer) would be a very good fit for CNJ as a result, allowing them to concentrate on attack magic at the expense of healing potency and spells (maybe they could have a trait that boosts attack magic potency even further if under the effect of Cleric Stance, or something).