I can agree with the all way too long Cooldwon for the short duration,
but as healer or BLM stainding in his leylines (that to me any time I use it seems like a "please fuck me" request to the whole enemies party) is an efficent way to land Fire IV on someone that is attacking you.
If they buff his effect in my opinion it will become probably OP, I would rather see a shorter Cooldown.

Instead I think it's time to remove the DMG buff on Retrogradation and Aura Blast and give some decent addictional effect to them (expecially Aura Blast)