Please take this post with a grain of salt. I think I may be overanalyzing things that may or may not translate into the live realms.
So what are we supposed to do? How are we supposed to heal? Tell us Blizz! Every time we think we have it figured out you turn us on our noses and tell us we are doing it wrong.
Single stacks of Lifebloom were a PvP tool. The one that made the resto druid the most feared creature in pre-wrath arenas. No matter what you did, that bloom was going to heal your target and there was nothing you could do about it, short of bursting him/her down or switching to another target.
Triple stacks were the purview of tree druids in PvE. Stack them on the tank and keep them rolling. Do not let them bloom. Do not collect $200. It provided a good amount of HPS (healing per second) and an amazing amount of HPM (healing per mana) giving us both throughput and efficiency. when WotLK hit and we all levelled our healers to 80, we found that higher ranks of lifebloom were not quite as efficient, but still provided both benefits they had enjoyed before. Coupled with a newly useful Regrowth and a recently nerfed, but still useful Wild Growth we learned to respond to burst damage and group damage in raids as well as only bufferring against it.
Enter the great lifebloom nerf of 3.1, stage left. Suddenly, our most efficient heal becomes our least efficient one. Suddenly, the dreaded bloom - the very thing we conditioned ourselves to avoid at all costs - becomes another tool in an already complex arsenal of healing tools. Suddenly, lifebloom in PvP gains a new life and becomes three times more powerful, at the significant cost of its efficiency.
So, I ask again: how are we supposed to heal? Obviously, the Blizzard game developers have something in mind for the druid. But what is it? We are no longer the rolling tank healer that we used to be. The 6-second cooldown on Wild Growth suggests we aren't supposed to be a full-time AoE raid healer. Rejuvenation ticks way too slowly to be an effective response to damage with any kind of burst potential, but can be used, in conjunction with other HoTs as the buffer it has always been thought of. Unglyphed Healing Touch is too slow and too expensive to use continuously and Nourish without a 4-pice Tier 7 set bonus is mediocre both in throughput and efficiency, as Phaele showed in her excellent breakdown a few months ago.
The answer, I think, lies in a combination of all the spells we currently have access to. Will we be the powerhouses of old? No, probably not. We can, if we so choose, continue to roll lifeblooms on tanks, but will face the prospect of spending the second half of any boss fight staring at an empty mana bar. No. Stacking lifebloom will no longer be the answer. Throw single lifebloom stacks around in the raid in a sort of fire-and-forget manner may be more forgiving since their ultimate blooms (whether they heal or overheal) will restore a portion of our mana.
I think the ultimate winners from this nerf will be restoration druids that heavily favor PvP. Their healing is going to see a jump in an arena where efficiency, though still important, takes a back seat to throughput. For the rest of us, Lifebloom in conjunction with a newly crit-friendly Nourish and Rejuvenation, as well as the occasional Regrowth, will characterize our new reactive style of healing and contrast sharply with the proactive approach we were always known for. Time will tell.
It goes to 11 (or 10)
4 weeks ago