There's some interesting discussion on the new Blizzard healing forums. One new line of debate I'm seeing recently is the effect of "smart" heals such as Chain Heal, Circle of Light, and Wild Growth. Each of these spells are multiple target spells, but the server chooses some or all of the targets. And the choice is not random. Instead, the server usually chooses the targets with the lowest health, maximizing the spell's effectiveness.
Unlike direct heals, where the target has to be chosen a few seconds in advance of the spell landing, the smart heals choose their targets at the time of the heal, making them perfectly reactive. What this means is that these spells tend to have much less overheal than spells which require human targeting. As any paladin can attest, our overhealing skyrocketed in TBC, to the point where seeing 50%-60% overheal is common.
It's very possible that because of their high effectiveness, smart heals are a better choice than most other heals, in any situation which does not require large direct heals. As well, a great deal of the skill in healing involves proper target selection, choosing the right person to heal at the right time. Perfect smart heals controlled by the server negate a lot of that skill.
One interesting suggestion I've seen is to give the various smart heals the Beacon of Light treatment. Essentially, the smart components would only work off the effective healing done to the selected target, not the raw healing. If you cast Circle of Healing on a full health target, it does nothing, just as if you had cast a direct heal on that target.
This would once again make target selection more important, and weight healing back towards the direct single-target spells. You can't just spam Chain Heal and expect the server to do perfect bounces, you have to direct your healing to where it is needed.