Personally, I'd like to be something similar like WoW (yeah worst game ever, worst example ever, whatever: bite me): In that game healers need spell power, which is given by Intelligence and it's a unique stat for all spell users, both dps and healers, and some healers like discipline priests work alongside this benefit by making their damage also their heals. In general however, spell power is used for both healing and damaging and the only difference is the secondary stat (which is not the case here)

Honestly I don't know why this couldn't be the case: MND could be a healer-only stat that increases both their spell dmg AND heals (with proper balancing though) and leave INT to actual spell casters like BLM and similar. Considering how straightforward this game is (one stat for one class), I wish this was somehow the case also for healers.

Perhaps one day Piety could become useful again with ideas similar like these!

P.S.:And if the issue now is that 10% bonus damage from cleric stance...well, that's what balancing is for isn't it?