I mean, in the end, isn't what they are doing essentially the same as downranking - lower cost mana spell that heals for less?

Yes. Actual downranking had two problems though. One, it was a pretty obtuse concept for new players. If you're super elite you might dismiss that concern, but it was something players had to figure out (typically be reading forums or something) and worked nothing else like anything in the game.

Even more of a concern, a lot of players downranked not only to conserve mana when they didn't need to heal much but because at some point in gear the coefficient starts to matter a lot more than the base points. They could essentially get a fairly powerful heal off at a lower cost.

We think the decision of when to use a big heal and when to use a small heal is a fun one -- it was fun for players for vanilla and BC. Healing might be too bland if you literally only had those spells, but nobody will.

The argument would be that a very weak but very efficient heal would result in that class always healing. I don't think that's a problem, or even counter to Blizz's intent. In fact, Blizzard has said that they do not want to go back to the model where healers spend half their time sitting there so that they can regen mana. Rather, they want us to be casting a lot; but they want the decision of what we cast and when we cast it to be more than "mash X button 50 million times".

We talked a lot about keeping the paladin model inverted, where the small heal is super efficient. There is probably a way it could still work. In the end we were just concerned that it would end up biting us in the rear. Somewhere along the way we'd have to make special rules to handle the paladin, who would risk being too mana efficient or too incapable of healing when forced to heal outside of their mana-efficient comfort zone. Could we have designed it? Probably. But frankly I'd rather spend our time on more interesting mechanics and spells. I'd rather the new AE heal really make paladins feel like they can AE heal rather than really making sure FoL felt small, cheap and fast. I agree it erodes a little bit of distinction among the classes, but only a little bit. There are far more interesting ways to make healers feel unique than in the relative mana efficiency of their small spell.

Divine Storm will get the Whirlwind treatment (less damage per target but unlimited targets).

The difference is that paladins fit their rotations around cooldowns while warriors do so around a limited resource. So it's entirely possible a paladin will still use DS when other attacks are on cooldown. (It will depend on what exactly the Ret rotation looks like, which we're still developing.) Divine Storm also provides a little healing too, so it's not exactly the same as Whirlwind. We probably wouldn't want to get to the point where Rets feel the need to have their single target spec without DS and the cleave spec with DS. (And without knowing the numbers, it's going to be difficult for any of you to insist that this will or will not happen.)

In general, we don't want buttons that are good against single targets to just be better against groups of targets. It makes rotations too static and makes numbers hard to balance since "cleavey" specs can do so much more damage against tight packs of enemies. Some higher damage is fine. It just too extreme right now.

These are previews, not patch notes. Just because we didn't mention anything doesn't mean there is no chance of it changing.