Based on feedback from this forum, elsewhere and our own brainstorming, what we are thinking about right now is something like a 6 sec cooldown for Circle of Healing and Wild Growth.
We're less concerned about Chain Heal, in part because it's not instant, prevents movement, falls off with multiple targets, and is the spell that shamans are supposed to be hitting, while priests and druids have many other spells.
At 6 seconds, you would still want to use CoH/WG in the right situations (though hopefully not *every* time they are up), but you'd also want to use other spells during the cooldown. To be fair, a lot of priests and druids are asking to push other buttons.
This sounds like a potentially scary change because it has a lot of ramifications -- one of the reasons we are mentioning it so early is to get feedback. We don't want Resto shammies to push other healers out of raids. We would change some of the encounters knowing that CoH spam was no longer possible.