Well as it stands now the amount healed is not much of a difference from CON to LNC, and yes I think it would be a safety net worth equipping in certain situations (like an event of sorts) but for general exp grinding, I don't think you should need to have a healing spell equip.

On that note, being that you can equip a spell whenever so long as you are not in combat, you could easily 'feel out' if you need to have the safety net or not, its not like you need to run back to town to the Moogle in your house to change your job.