Much of THM's storyline revolves around the ability to resurrect... a healing ability.

At the end of the day, if you're trying to prove that THM was never meant to heal, they wouldn't have been giving a healing spell, and then had that healing spell buffed. The best you can argue is that CNJ was supposed to be a better healer, which does not mean that THM should not heal any more than the existence of WHM means that RDM should not heal.

It's fine to say that THM is not going to be able to heal in the future without trying to rewrite history. This game was intended to have two healing classes at release.