#0 - April 14, 2010, 7:30 p.m.
In my opinion, this is a flawed structure. While there may be varying degrees in the sizes or efficiencies of each of these heals, structuring it in that way still provides a relatively homogenous core. That means two things:
(1) The core activity of those healers feels relatively similar.
(2) Each healer will be differentiated based on the secondary spells and utility they provide.
This is a potential problem in a number of ways. First, it does tend further toward homogenization, which isn't fun for most. Second, it requires reliance on other healing spells to define each class; if those spells are not useful a high percentage of the time, or if one class has relatively few of such spells, things get still more boring for the healer.
How do you get away from that? Three ways that I can see, really. The first is to adopt an approach like that taken with druids. Druids have three direct single-target healing spells as well; and technically, one is small, one is medium, and one is large. What makes druids well-structured in this respect is that each heal is unique not just in size, efficiency, and cast time, but also in terms of mechanics--Nourish requires setup and planning for maximum throughput/efficiency, Regrowth reflects a druid's proactive nature and is only maximized when used on targets who will be taking more than that single spike, Healing Touch is a big one-off that a druid otherwise lacks. The other healers currently lack this kind of differentiation between spells, so far as I can tell.
The second is to emphasize synergy between core abilities. Druid heals, again, have a degree of this synergy - Regrowth boosts Nourish and can fuel SM - but even that doesn't go too far. Shammies and Pallies have some synergy between healing spells, but only by stepping outside the bounds of those core spells (HS and RT) and/or adding an extra spell to the mix (SS+FoL). What if Beacon interacted differently with FoL versus HL--say, FoL was copied, but HL cast directly on the Beacon target either made it into a small AOE (like the current glyph) or put a shield/additional buff on the target? What if Flash Heal on a target with PW:S increased the amount absorbed by PW:S instead of actually healing the target? What if Healing Wave put a stacking buff on the target that, when it hit 10, proc'd a CH originating from the target? It's pretty easy to get creative here.
The third is to not stick with the strict "small-and-inefficient, medium-efficient, big-and-slow" model for every class. What if one class had a small, efficient, quick heal, like pallies have had in BC and WotLK? Lately, we haven't used it much because the throughput is low; but if we had more time to get more heals in before the target was to drop, we'd use it more often. What if one class had a big heal that was also very fast, but which was even more expensive than the big heals of the other classes? If mana is an issue in Cata, that's a self-regulating issue--that'd become the best class for getting the huge emergency heal through, but they'd be able to turn to it even less frequently than others. Departing from the standard structure of speed+size+cost for different classes isn't necessarily a bad thing at all.
It is entirely possible that, as someone who primarily plays as a pally healer and is used to having those "core" heals as its only tools, I may be biased. I also may be biased because, as things stand, we have the fewest tools outside of that core set. But I know that I, for one, would be a great deal more excited for Cata if there were synergy between core heals or other interesting secondary effects. I'd also be more excited as a raid leader if there were a distinguishable difference between the core healing styles of each of my healers, even as to their most similar spells. As it is, even knowing that we've only gotten a taste of the changes to come, I'm nervous about being reduced to a healer who has the same types of efficiency-speed-potency heal categories as every other healer, but fewer additional healing tools to supplement it.
Just my preliminary big picture thoughts.