If there are serious wounds that the Heal spell can't manage any more, then this spell replaces it. Great Heal is much better at treating these wounds, although of course it also costs much more in terms of reagents and mana. Note however that like Heal, it doesn't treat poisoning, only physical wounds.
If even this isn't enough, then only Restoration can help.
Whole health restored; full vitality given; such is the nature of Vas Mani. A miraculous spell requiring concentration and vast knowledge of anatomy, Vas Mani is reserved for experience mages. Vas Mani fully restores patients from combat wounds. While it provides neither antidote to poison nor cure for disease, Vas Mani does heal all damage wrought by these ravagers, ensuring survival until a cure can be found. The difficulty in preparing Vas Mani is in locating the mandrake root; otherwise the preparation is straightforward; mix the mandrake root with ginseng and spider silk. To cast Vas Mani successfully, the caster must concentrate totally on the subject to be healed. When the concentration is full, one can actually see wounds heal. Because the healing process can take several hours, Vas Mani cannot be used during combat.