Correction: Once again foiled by bad information on the net. While I think the essential point of my post is still completely valid, the casting time of Healing wave is indeed 2.5 seconds with the proper spec, not 2.
As Cataclysm was approaching, the developers talked about how they wanted to change the way healing worked. They said they wanted to "slow it down." What exactly it means to slow things down, however, might not have met the expectations of everyone.
Healing in the Wrath environment could certainly not be accused of being slow. Commonly people talked about how healing was all about twitch reflexes. You twitch wrong, someone dies. You twitch right, everyone is back at full health and everything is fine.
I wondered as Cataclysm approached how slowing things down could keep things challenging. After all, successful Wrath-era healers were used to making a life-or-death decision every second. If we only have a make a life-or-death decision every two seconds, how could that be anything but easier? It turns out that slower did not mean exactly what I expected. In the sense that nearly every GCD was life or death things were very fast in wrath. In the sense, however, of the amount of damage your raid took compared to the amount of healing you were capable of doing, things were actually incredible slow.
In Wrath healing, druids and paladins would often have overheal in the 60%-70% range, or even a little higher. Discipline priests had fairly low overheal, at 30%, but when you looked closely, because shields could not overheal, their actual overheal on spells that healed people could get just as high or sometimes even higher than paladins and druids. If you are overhealing 70% and no one is dying, that means you are outputting three and a third times as much healing as is needed. In a 10-player raid, that means that one healer is able to output enough healing to keep the entire raid alive. The reason you brought more than one healer was a question of distribution, not of throughput.
In a Cataclysm raid overhealing 70% would be next to impossible. You would pretty much have to go out of your way to target people at full health with your heals to achieve a number like that. Distribution of heals is no longer reason you bring three healers to a fight, you bring three healers because you need that many to actually heal the amount of incoming damage.
This was easiest to see in early experiences healing heroics. When the entire group had just reached item level 3291 healing through boss damage could be very difficult. The boss could actually output more damage per second than some healers could heal. The reason it was possible to win was that the damage coming from the boss only exceeded the ability to heal by a small amount. If the fight lasts three minutes, and your group has around 550,000 health between then you can actually win if the boss does 3000 more dps than your healer can heal.
This is a new kind of calculation, one that we would never have done in Wrath of the Lich King. This is what it means to "slow down" healing. Instead of needing to land a heal every second to make sure the boss doesn't two-shot the tank, you need to maximize the amount of healing you can get over a long stretch in the hopes that it will be enough total healing to give the dps time to win the fight.
Many of us, when we heard that they were going to make mana matter, rightly reasoned that if the total amount of damage that will be done before the fight ends is close to or slightly exceeds the maximum amount of healing that your healer can do over that period of time then your healer cannot afford to use low efficiency heals. The flip side of this – which is entirely necessary for the new healing model but which I didn’t see coming – is that if the total amount of incoming damage per second is close to or slightly exceeds the maximum amount of healing that your healer can do per second, then your healer cannot afford to use low throughput heal.
A lot of priests have taken the wrong path here. For a shaman, the real question was how to do enough healing over the length of the fight, and Healing Wave was an important part of the answer. But let’s take a look at Healing Wave. Its casting time is only 2 as opposed to 2.5 for Heal, but its scaling is similar to Heal and while its base healing is lower it is higher on a per second basis. Tidal Waves hastes it by 30% twice every six seconds. It can trigger Earthliving Weapon. Ancestral Awakening matches Divine Aegis in the extra critical department and Nature’s Blessing probably slightly exceeds Grace in a heroic dungeon. If you are having trouble keeping up with incoming damage than Deep Healing increases its effect by around 1.25% per point of mastery while the discipline priest mastery likely increases Heal by around 0.1% per point. The tank also has Earth Shield. All together, Healing Wave is slightly more powerful than Heal, and has an average cast time of around 1.7 seconds to Heals’ 2.2 seconds.
For a discipline priest, the question was never how can I do enough healing over the course of the fight, it was always how can I do enough healing to keep up with the incoming damage on a per-second basis. With 15% extra intellect, Hymn of Hope, Rapture and Shadowfiend, discipline priests have enough mana to get through the fight, what they need is enough throughput to get through any given 10 second period.
So the solution is to just not cast Heal. If you are trying to heal damage to a single target, cast Greater Heal. If you are looking to fill time casting something because you don’t think you can afford to waste it, cast Prayer of Healing - you can think of it as a single-target heal with benefits rather than a group heal if you need to. If everyone is near full use Renew. If none of these is a good option then just don’t do anything at all. This may sound like a strange suggestion given that I’ve been talking about not having enough throughput to keep up, but casting Heal can be worse than nothing. Given that Greater Heal has about 2.8 times the throughput of Heal and an at-par mana efficiency Prayer of Healing has around 2.9 times the throughput of Heal, starting a heal now instead of waiting one to one and a half seconds to cast a better spell is a loss of throughput.
Strangely enough I don’t even think this is a complaint. For Heal to be a bad spell for discipline priests – and I think a questionable one for holy priests – is not that bad a place for the game to be. Priests actually have a lot more spells than the other healing classes, and expecting them to use them all is a little unrealistic. We should be much more concerned about the relative weakness of Power Word: Shield for discipline and Renew for Holy than about Heal which I feel completely comfortable leaving in my spellbook to be pulled out for Chimaeron.
1. And many of the members of your group may have faked their way to item level 329. This is especially easy for most tanks since, as plate wearers, they can easily buy a whole bunch of gear that is absolutely useless to them from faction vendors. Cloth with spirit counts towards a prot warrior's item level.