About the healing. How about some sort of "healing sickness". For example, if I heal an ally, it'll heal for the full amount, but will add a debuff that stacks up to three times and decreases subsequent non over time heals by 30% for X turns and maybe persist through combat.
Heals are still somewhat viable like that, and you have to play around when using then to avoid getting huge debuffs on character, it also makes food outside combat more valuable.
The problem with that is that healers will become potentially much worse.