A point into healing probably won't help you cross the hot rocks because you stop moving when casting the healing spell. You need to drink a potion as soon as you enter the lava area.
I just checked and Ghosts can be summoned and will heal you in areas with no enemies around. (And then I entered an area with enemies and died because the ghost didn't seem interested in healing me, but that's beside the point.)
The idea is to cast Healing BEFORE you move onto the rocks. Healing heals over time, just like potions (and I've had situations where potions alone didn't cut it for the lava).
