Hmm.... I definately like the idea of manifest zones where healing magic is possible (albeit, I would rule at 50% efficiency max), and the idea of special herbs allowing some boosted healing from the heal skill, and the heal skill working 'normally' as well.
The Tear of Cyre sounds really cool, but I would definately want to restrict it's use greatly to keep the Mournland a place of despair and difficulty. I would rule that only the one who holds the tear itself can channel healing magic through the sphere into ppl to be healed. Thus, only one caster can make use of it, and for a limited amount of spells per 48 hour period. Also, I would make the item very rare and difficult to make, maybe requiring Khyber dragonshards recovered from beneath the Mournland itself within which a living spell of healing must be bound or something along those lines...