White Mage: MND, DET, PIE, HP, CRIT, SS
Scholar: MND, CRIT, DET, HP, PIE, SS
What do White Mages have trouble with?
- Mana & Mana regeneration
- %Healing through debuffs
- Enmity

How can I alleviate those issues?
- Increase PIE
- You can't
- Improve playstyle

What do SCH have trouble with?
- Raid/group healing
- Limited HoTs

How can I alleviate those issues?
- You can't
- You can't

Summary
The only stat increase you can take to reduce pain-points for either healer is piety.