I think 4th Edition's healing mechanic is not flawed and works well. Just as one small example, clerics get to spend a minor action to let an ally improve their healing surge value by a substantial amount. There are almost never better options for a cleric's minor action than a healing word. Quick Draw + healing potion is just as good, if costly. Second Wind is supposed to suck - it makes healing powers worthwhile. If you heal instead of doing something else, that's just one more ally that's not bloodied and still in the fight. Sure, it might have been more effective toward getting the BBEG killed to stun him (preventing more than a healing surge's damage), but then you're running the risk of losing one of the party for good. You trade off efficiency for acceptable risk.
I don't think the same should be true for 3.5 D&D however. Healing an ally should be just as good (if not better) than casting a spell that does damage. It could be better to paralyze an enemy, but I prefer to compare healing to damaging spells.
I'm glad this was brought up; there are few things to me that are more frustrating than the 3.5 Cure spells' healing progression. This is what I might do to them:
Cure Light Wounds - Heals caster level x 3 + 2d8 points of damage and an equal amount of nonlethal damage.
Cure Moderate Wounds - Heals caster level x 4 + 2d10 points of damage and an equal amount of nonlethal damage.
Cure Heavy Wounds - Heals caster level x 5 + 4d6 points of damage and an equal amount of nonlethal damage.
Cure Serious Wounds - Heals caster level x 6 + 4d8 points of damage and an equal amount of nonlethal damage.
Cure Critical Wounds - Heals caster level x 7 + 4d10 points of damage and an equal amount of nonlethal damage.
Cure Wounds - Heals all lethal and nonlethal damage to a target.
That's spell levels 1-6 for clerics.
I arrived at these numbers by comparing the following:
Flamestrike damage, straight sneak attack damage without extra feats or weapon damage, average barbarian damage.
Cure heavy wounds heals twice this average, and every other level of the spell heals either less than this or more than this.
Result: ALL healing spells are viable at every level as healing spells (compared to a 1d8+5 from levels 5-20), but the most costly spells (ie: higher spell levels) do better healing. Also, healing is far more reliable. Downside: an empowered, maximized
Cure heavy wounds would do (lvl x 5) + 24 + 2d6. That's an average healing bonus of only +17. That is pathetic for making it a spell even 2 levels higher. But, that's not all bad, as it gives an incentive to quicken healing spells instead.
Average healing for a level 12 cleric:
1st level spell:
Cure Light Wounds - 45 hp
2nd level spell:
Cure Moderate Wounds - 59 hp
3rd level spell:
Cure Heavy Wounds - 74 hp
4th level spell:
Cure Serious Wounds - 90 hp
5th level spell:
Cure Critical Wounds - 106 hp
6th level spell:
Cure Wounds - All hp.
Compare this to average hit points for level 12 characters:
cleric Con 14: 81
fighter con 18: 118
barbarian con 22: 155
This might be too much healing, as it would result in fights having the potential for being much longer than 5 rounds.
Tone it way down thus:
Cure Light Wounds - Heals caster level + 1d10
Cure Moderate Wounds - Heals caster level x 2 + 2d6
Cure Heavy Wounds - Heals caster level x 3 + 2d8
Cure Serious Wounds - Heals caster level x 4 + 2d10
Cure Critical Wounds - Heals caster level x 5 + 2d12
(7th or 8th level)
Cure Wounds - Heals all