So I did.
My conclusion is that from the standpoint of raw healing output there’s nothing better I can do in six seconds than cast Tranquility but that it doesn’t always matter.
Warning! Questionable attempt at Theorycrafting follows.
I did not look at how these spells scaled with more spellpower.
Because most of the spells don’t crit I just worked out how much each tick was and then plotted the appropriate tics of everything on a timeline. With Nourish I plugged in the lower and upper values to get a range.
Additionally, apart from the occasional VoA PUG I don’t do 25-person content so my talents, glyphs and spell-choices are tailored towards 5- and 10-person groups.
Tranquility: Heals each person in the party for 6181 every 1.5 seconds or so. Lasts roughly 6 seconds. Long cooldown.
Wild Growth: Heals the five (or six with Glyph of Wild Growth) lowest-health party or raid members in range of target. Ticks every 1 second for 913 – 689 (decreasing). Lasts seven seconds with a six second cooldown.
Rejuvenation: I have Glyph of Rapid Rejuvenation so this ticks for 2480 every 2 seconds. Lasts 12 seconds. When healing an individual I like to cast Rejuvenation and then decide what to do. I should write an article about how much I like casting Rejuvenation.
Six seconds of love
Assuming Tranquility hits five targets, it heals for 123K compared with 39K healed by the other spells. In fact, even if Tranquility only hits two people it still comes out slightly ahead in that time,though it seems implausible that Tranquility could hit two people and Wild Growth five. Glyphing Wild Growth doesn’t really affect things very much in this case.
However, since each person is healed for almost 25K, in most fights some of it is going to be overhealing.
Additionally, at the end of a Tranquility cast, I have no one HoTted. So what happens after this? Have I bought six seconds of time but now everyone is going to die anyway?
Now until this, it hasn’t really mattered whether I was talking about a raid or a party. However, what I do in the next six seconds will depend on the group size.
If I started off with Wild Rejuvenation and I am in a 5-person group, I’ll probably throw another Wild Growth out there (since the cooldown is up) and then toss out some Nourishes, I assume since I was thinking about Tranquility in the first place there is a lot of damage going around and everyone is still Rejuvenated.
However, if I am in a raid, I’ll likely keep going with the Wild Rejuvenation method, starting with people who are not in my party and therefore missed out on the Tranquility.
In the raid case, the Wild Rejuvenation approach has caught up quite a bit by 12 seconds, lagging behind the Tranquility case 163K to 119K. By 18 seconds, this gap has narrowed to 15K healing, which is where it more or less stays.
In a party it’s a little different. Unless pets have sneakily grabbed Wild Growth charges (which frankly they do all the time) each party-member should have two HoTs on them by the time you start casting Nourish.
With two HoTs, my Nourish hits for 7.5K and crits for 11K. After 12 seconds, this puts it between 13K below the Tranquility method or 2K ahead of it.
After 12 seconds I need to start refreshing Rejuvenation.
Extension to 25-person raids
I haven’t done the math properly on this because I don’t have a) a good spreadsheet or b) a strong desire to tweak my spec and glyphs to test this thoroughly.
In place of math I offer hand-waving and supposition.
If I had a more raid-oriented setup I would have Glyph of Wild Growth rather than Glyph of Rapid Rejuvenation. This would decrease my throughput slightly but let me keep Rejuvenation on more people, which is good. I’d therefore expect the Wild Rejuvenation case to take a little longer to catch up but not really differ that much from how it looks in the 10-person case.
If you have three to five people in one party who will benefit from 25K healing over 6 seconds, Tranquility wins hands down, particularly as the number approaches five.
Over 12 seconds you could heal the same five people for about the same using other spells.
Over 12 seconds you could heal ten people for a decent amount more using Tranquility than not using it.
Over 18 seconds there is not a great deal of difference between the amount healed by either approach.
I think where Tranquility is really useful is when something has gone wrong — players are at low health and more group damage is imminent. In those cases, I should really remember to use it.
However, there likely aren’t many where using it routinely is necessary and I don’t think I’ll play around with reducing the cooldown again anytime soon.
Does Tranquility heal pets? I haven’t been able to find this answer online and haven’t had a chance to test yet.