Okay, so after I wrote the second half of this post, I saw that GC had just posted about downranking heals here:
We were spending more and more of our design time trying to make sure that the lower ranked spells didn’t always trump the higher ranked spells since with enough spell power etc. the coefficients start to matter a lot more than the flat value of the heals. We kept nerfing the coefficients over and over and could have kept doing that, but at some point we asked ourselves why so much of our healing design time was spent balancing downranking when it was a pretty obscure concept (from a new player perspective) in the first place and we were having trouble getting healers to use their entire arsenal of spells.
We recognize that there is some fun in matching the right heal to the job, and we would love to add some smaller heals back to the game, but first we have to get the balance right where huge, fast, expensive heals don’t always win. Otherwise, offering you small, cheap heals won’t do anything.
So, this is interesting because currently the only time you would want to downrank your heals is if you cared about how much overhealing you were doing. There is only one encounter for end-game raiding where it is actually possible to heal too much:
Anub in Trial of the Crusader has an interesting final mechanic. In the last 30%, he has the ability to heal himself based on 10% or 20% of the total health you have at that second. If you keep everyone healed to full, that means the boss is healing a lot. If you keep people around 50% health during that phase, you end up with the boss healing for half as much as he would otherwise. With the relatively short enrage timer, you really don’t have the ability to let him soak up our health like a sponge until you can out gear the encounter. The boss also does enough AOE damage to the raid that keeping them alive can be a bit of a struggle if you can’t use big burst AOE heals on them.
One thing that looks like it could help with healing for the last part of the Anub fight as a druid could be to pull out lower ranks of some spells (ie. rejuv & wild growth), so that you could have more control over their health more. In our 25-man (non-heroic) kill this last week, I actually found that using my max rank rejuv had a habit of keeping them higher health than I wanted, but if I dropped down to a low rank of rejuv, they still got a decent sized heal from my tier 8 set bonus, without as big of a HOT at the end doing more than I wanted it to. A downranked wild growth could heal for enough to keep people from dieing, but not enough to keep them topped off at full. There is (unfortunately) only one rank of nourish…
I used max rank heals for everything before that, and I used max rank HOTs on the tank for that phase (they take a lot of dmg). You also wouldn’t really want to use rank 1, as there’s not enough oomph on the HOT portion. Also, you don’t save any mana by using lower ranks. This is also probably the only place currently in the game where using lower ranked heals is to your advantage. However, this is also NOT for beginners. Figuring out the right size heal to use is tricky… and you may need to try it a little bit before you found something that worked the best for your raid. (and as Bai points out, for the hard mode/heroic versions of the fights, you may need the highest ranked spells – you also want to keep people at a higher health % for hard mode compared to normal).
You also won’t be able to take advantage of this for long, given the incoming tier 8 set bonus nerf, along with downranking becoming impossible in Cataclysm once they take away the ability to buy new ranks of spells as you level (you’ll have one rank of each spell that just scales with you every time you level).