Lifebloom: Mana cost of all ranks doubled. When Lifebloom blooms or is dispelled, it now refunds half the base mana cost of the spell per application of Lifebloom, and the heal effect is multiplied by the number of applications.
What this means:
In ToL/with talents and 2pc T7, Lifebloom (hereafter referred to as LB) costs 366 mana. In 3.1, it will cost 732 per application. That means that it will cost 2196 mana to establish a triple stack, and then 732 mana to refresh (either 9 or 10 seconds, depending on your glyphs).
If you then allowed that triple stack of LB to bloom, it would refund half the cost of the 3 stacks, and give you a triple-sized bloom at the end.
In my gear (with just MotW, no raid buffs etc), my LB is 392 healing per tick, 1176/sec rolling triple stack. It blooms for 3217. In 3.1, it would bloom for 9651 (obviously quite a lot more if I had raid buffs and consumables), or 14477 crit (wow). The stack would cost you 2196 to establish, and would refund 1467 mana.
So basically you can allow your LB to "bloom" for ~10,000-15,000hp (more with raid buffs) and a 1467 mana refund. Remember though, that you will need to re-establish your triple stack or you are losing 1176/sec ticks, plus Nourish heals will be smaller if LB isn't on your target.Also consider that if you choose to heal this way, you might opt not to use the Glyph of Lifebloom because you might prefer to have a shorter LB. You could also remove 1/1 point in Nature's Splendor to shorten it even further - but consider that this will affect your other HoTs, so I wouldn't recommend it.
Despite the fact that this 10k heal would be hard to control, it might be good in an emergency to opt to let it go.
The basic changes
In raid healing, if you happen to toss a LB to someone to smooth out their health, it will bloom for the same amount as before (single stack = no multiplier on the bloom), and refund you half the cost. So, if you're using LB on the raid, it will be the same cost and healing as it is now - there is no nett change.
If your style is to roll LBs on the tank/s, it will cost you double to establish and to maintain your stacks. This will obviously have a marked effect on your mana, particularly if you roll on more than one person. You may need to lean more heavily in favour of regen gear/consumables, save your innervate for yourself (and possibly consider the Innervate glyph - although I'm not sure what I could swap out for it). It may also make staying in 2pc T7 more attractive for the 5% LB cost reduction.
To put it very simply:
If you allow your LB to bloom all of the time, your mana efficiency will say the same, but your nett healing output will likely go down. You will lose healing through the loss of ticks and having to re-establish them, plus the fact that your blooms may end up as overheal because you can't easily time them (on fights where your target is taking heavy damage, the bloom is more likely to end up as effective healing).
If you roll your LBs most of the time, you will have the same healing throughput as you do now, but lose mana efficiency, which will be magnified if you roll on more than one target. It will cost you double to refresh your LBs, and will only ever get a little of that back if you accidentally drop your stacks. You will need to carefully consider how many people to roll LB stacks on (most likely only people taking constant, heavy damage, to warrant the high cost).
GC has responded to questions about the change here. To paraphrase his major points:
Rolling Lifeblooms on 2-3 tanks is just hands down one of the most -- probably the most -- efficient heals in the game. We didn't want to nerf the amount Lifebloom heals, but we were concerned druids would jump to the top of the healer stack pretty quickly with the recent mana changes.
We think rolling is a fun part of the spell. It's just too efficient and makes Lifebloom the best heal per second and heal per mana.
We don't want (rolling on multiple people) to be very efficient.
Now it does potentially give you a new healing style, where perhaps you roll the 3 stacks on the MT but do 3 stacks and let it bloom on the OT. You can imagine a Patchwerk scenario where the MT is taking damage consistently and the OT takes it in bursts. The traditional roll is more expensive, but keeps the healing per second high and consistent. Allowing for a bloom is more mana efficient at the expense of having the hot up 100% of the time.
We have done a lot of calculations on this, but we also need to see how it plays out in Ulduar on the PTR in a real raid scenario, as well as seeing if any theorycrafters can poke holes in the model.
So, basically, they STILL consider rolling on multiple tanks to be too good (too efficient) and while they want us to still have that power, we need to consider more carefully when and how to use it (and on how many targets).
My initial thoughts
I'm disappointed that we're being nerfed again. I don't think we need another hit to efficiency, and I don't think we need something to discourage us from rolling LB. While I agree that LB was a little overpowered in the Hyjal days of rolling on 4 or 5 people and ONLY doing that, I enjoy rolling on a couple of people and I think it makes our healing interesting and challenging. Unfortunately it would appear again that Blizzard's definition of challenging is "more of a pain to do". I think I will still be rolling LB on the tank, but this will definitely discourage us from rolling on a couple of tanks, because the cost will be prohibitive.
This is my healing style and it concerns me that I might find myself struggling for mana and unable to roll on two or more people. For now though I am going to adopt a "wait and see how it feels" approach.
Despite the inefficiency of doing so, it does give a nice little option that if your triple stack is about to expire and you see that the target could use a 10k heal in a hurry, let it go.
Personally I think I would rather refresh the stack and toss a Nourish or Regrowth, saving the trouble of having to re-stack LB to 3; but it's an option. On fights like Loatheb there always seem to be people falling lower than others (eg, ret pallies), so you could double or triple LB them and time it to fall off when the aura lifts, meaning they will get an automatic 6-10k heal while you're busy throwing WG or healing the tank. I can see this being quite handy, albeit extremely situational.
Normally though, you can't really ask, "Will my target need a heal in 10 seconds' time?" and it would be hard to use this proactively. It would be almost impossible to know whether your 10k bloom will be helpful, or merely end up as overheal. I think instead it will more be a case of waiting until almost the end of the LB cycle to see if a 10k immediate heal would be helpful, and letting it bloom (again keeping in mind the loss of your 1100ish/sec ticks, the time to reapply, and the loss of +healing to your Nourish until you get LB back on).
As an aside, it's also a nice consolation for the times that your LB accidentally drops off because you had to switch to healing someone else in an emergency, or you were out of range, lagging, etc. A 10-15k cushion of healing and a small mana refund while you get back on track. Where normally losing a stack would be too bad, this is a little bonus.
Now we wait for release
GC has said that they will consider tweaking the numbers if testing reveals that the change was a little heavy-handed. The best we can do is get as many druids onto the PTR to test how this change will affect us. Other than that, we'll have to wait and see if this change goes live as-is.