I don't want to go back to the faceroll that was WotLK healing, and neither does any other PVP healer who has been told "your spec takes zero skill to play". I'm enjoying using three bars of keybound spells now, mixing it up every now and then, finding what works. The problem I'm seeing is that as I learn more and more about when to time my heals, I'm learning more and more that even at the smartest most efficient level of healing, we are still running OOM one or two more times than we need to.
For druids, the lifebloom single target change and the super expensive rejuv mean when AOE damage hits (and it always will, in dungeons AND pvp), no matter how skilled we are, we will be losing mana, and fast. For me, I know there's a problem when I have the dps targeted, waiting for those 3 lifebloom stacks to bloom on the tank before immediately applying to the DPS taking the damage (timing lifebloom blooms, by the way, is one essential aspect to our new role, and it's quite fun to learn, but in this case, I'm having to use lifebloom on a DPS, risk wiping the tank, and the whole idea of it seems a bit panicky :P).
Going into Tree of Life form doesn't really help me enough for it to feel like an awesome CD. Why? Insta-cast regrowth isn't worth much when regrowth is the least efficient heal in the spellbook :P. Lifebloom on multiple targets is probably the best benefit it gives at the moment, which is fine, but meh, lifebloom takes time to cast, and time to heal, and three stacks on each of three dps taking massive damage really isn't practical. Essentially, it's become less effective as a panic button than, oh, say, innervate for instance. The spell itself is fine, but the mana mechanic dampens its awesomeness to a great extent.
The solution? That's a tough one. I'm getting a sense for just how sensitive those mana cost numbers are. Perhaps you should up the benefit of spirit to somewhere near where it used to be? Or perhaps introduce some mechanic that causes heals to do more healing as a healer's mana pool gets closer to zero. (Some passive for healers like Vengeance is for tanks, scaling up to something like 15%). That way, since health pools are huge, when we run OOM, our heal numbers amp up just a little bit to give us barely enough of a window to get the mana back for that last healing touch (or whatever respective heal each class has).
I don't claim to be a top-tier healer by any means, but a slight tune-up, I think, would get us to that "smart healers benefit, bad healers lose" state.