O.k. So I'm sick of reading post after post of:

We don't want to run out of mana and...

We don't like to just sit there doing nothing.

So what is wrong with an Active Regen Model: Meaning: Each class is given a talent Deep in the Healing Trees that:

Holy Priests: Any Direct Damage Holy Spell returns mana equal to 50% of the damage inflicted.

Disc Priests: Penance now restores mana equal to the damage inflicted on the target.

Shaman: Nature Spells return mana equal to 50% of the damage inflected.

Paladins: All instant cast abilities return mana equal to 50% of the damage inflicted.

Druids: (Assuming the remove Tree of Life) - Nature Spells return mana equal to 50% of the damage inflected.

This does quite a bit to make Healing "Fun"

Mana can Remain Relevant without being boring.

When players out-gear an instance, the Healers still have something to do.

Players need to decide whether they need mana or healing more at any particular moment

Encourages players to not "over heal" because they are not only losing the mana from the heal, but also the mana from not casting a mana regen spell.

Forces healers to stay situationally aware, as opposed to the unit frame tunnel vision.

Could theoretically bring back "healer rotations" w/o the boring aspect of just sitting there doing nothing.

Anyhow, just my thoughts.

I'm not sure we'd ever do a "deal damage to heal" model. It might work for new classes, but feels like a big change to existing classes that players know and love.

Having choices to get mana back is good. Standing around to regen mana is bad.

However, we still ultimately need a way that healers who are playing badly, trying to keep alive an undergeared / underskilled tank, or just tackling content that they're not yet ready for, can run out of mana to the extent that the encounter is over.