I think that (hooray) class differentiation has changed enough that both Where and Yokie are correct here. Certainly pre-2.0 (or 1.9 or whenever it was), there was a dominant strategy to use downranking. The change made it less dominant, but especially for long fights I'm not sure if it can be categorically stated that there isn't some downranked version that is over time more mana efficient.
My understanding of healers is this (ignoring "group heal" spells that aren't really relevant to MT healing)
1) Pallies have a short, cheap small heal (Flash of Light) vs. a long, costly, big heal (Holy Light)
2) Druids (Tree of Life) have an moderate, instant pure HoT (Rejuv), a short, costly hybrid HoT (Regrowth .. instant cast then a small HoT), and a unique HoT (Lifebloom) that is a very small HoT with a "bloom" at the end (but the "right" way to use the spell in raids is to build up a stack of 3 and sustain it, because it gives a sustained stream of healing for low mana)
3) Druids (Dreamstate) have a costly, big slow heal (Healing Touch) plus the HoT options. You don't see dreamstate druids in raids much b/c without spell haste gear, Healing Touch is just too slow.
5) Shammies have a small, cheap HoT (Totem), a medium heal and a big heal.
6) Priests have a mix of the big/small heals like pallies, plus HoT options plus stuff like PoM that I don't really know how it works.
Anyhow, healing has become more than just spam "fast small cheap heals" vs "big slow costly heals." Worry less about general rules across all healers, and know how to best heal with your class, given the role you've been assigned for a given boss fight. I know that for me, as a resto druid, it's not about "big vs. small" heals, it about keeping a steady stream of HoTs up on the MT. In theory I can achieve
1) 3-stack of Lifebloom, trinketed up, fully buffed and with ToL bonus: 800-1000 heal tick per second, at cost of only 220 mana every 8 seconds.
2) Rejuvenation: ticks about 500 every 3 seconds, at cost of 415 mana every 12 seconds
3) Regrowth: 3k heal plus ticks of 300 every 3 seconds, at cost of 880 mana every 21 seconds
Now I should be able to keep all of those up on a single target indefinitely. In an average 10-second period, that would be:
1) 10 x 900 = 9000 healing from Lifebloom
2) 3 x 500 = 1500 healing from Rejuv
3) 3 x 300 = 900 healing from Regrow (with an additional 3000 every other 10-second period)
So that's roughly 12-15K healing from just me every 10 seconds ... and because it's HoTs, it's largely independent of silences. That would have healing Sandric for half the damage he took during the 10 seconds of Gruul death he experienced. Instead, however, I wasn't healing him, I just had a 2-stack of Lifebloom up for 467 every second so I did more like 4500 healing, about 1/3 of potential.
And given silences, shatters, and cave-ins, I'll probably never sustain 12-15K healing per 10 seconds indefinitely. But Avesther's post earlier nails it -- what we need is some more strategic thinking in our healing assignments. If I'm focusing on just MT healing, I should be able to at least get 2/3 of that rate up (say, 9K healing per 10 seconds). If we have 3-4 healers doing that (achieving whatever the best way for their class is to achieve it), that's 27000-36000 healing per 10 seconds. That should keep any MT tank long enough for the DPS to do their job, even with cave-ins, silences, shatters, overhealing, lag, and whatever. But when those four healers are not focused, we can have the kind of gaps that killed Sandman that other night.
It's just like in BGs ... AC can have the top 3 damage and the top 3 healers, but lose horribly if all they're doing is fighting in the middle and letting the horde cap towers and flags. If we have healers each doing their own thing, the main goal ... keepign the MT up ... gets lost. With better healing coordination, we should be able to do much, much better.
Until its needed that is, the end of gruul you need a lot more than 2600 heals as your "big heal" like sandric showed but to say "NEVER" downrank in a raid is silly, do you let the DPS die or waste a 6k heal when they need a 2k topoff to avoid a fluke death?
yup