Our mastery bonus, according to the latest word from the Cataclysm beta, will place absorb shields on targets of our heals. The shields will absorb 8 percent of the amount of the original heal, with that percent scaling higher as we get the mastery stat on our gear. Currently, priests are the only healers with any sort of absorption effect. They've got both Power Word: Shield and Power Word: Barrier, though these are actively-cast absorption spells. Discipline priests also produce shields when they critically hit with a heal, via Divine Aegis. Our effect is clearly different from these, and actually has more in common with a few items than it does with an existing spell or talent.
Absorption bubbles are nothing new
You're probably familiar with Val'anyr, the only healing legendary and the symbolic healing weapon of Wrath. It has a proc that allows for our heals to produce bubbles on our targets, which is exactly what our new mastery bonus will accomplish. Val'anyr may be the example most embedded in recent memory, there was actually an item long before Ulduar that yielded the same effect. One of the optional bosses in the Temple of Ahn'Qiraj, Viscidus, dropped a trinket called the Scarab Brooch. It produced the same messianic effect, turning healing into bubbles right before our very eyes.
The problem with both the legendary and the trinket is the fact that they both had limited uptime. Val'anyr's effect was only active a percentage of the time, meaning it could proc at an inopportune time. The Scarab Brooch's long cooldown actually makes it more effective to use as an "external tank cooldown" rather than a part of our normal healing strategy. Our mastery bonus is currently worded to be a passive boost at all times, which changes the way we think about it. Blizzard also removed Sacred Shield from our toolbox, so it's clear that this mastery bonus was intended to be our prime source of preventative healing.
Our mastery bonus is powerful
It's easiest to model the bonus as a static 8 percent boost to all healing done, even overhealing. The true potency is actually far greater. It allows us to raise effective tank HP, and means that not all overhealing is wasted. I am particularly interested to see how it interacts with Beacon of Light. If the transferred Beacon heal produces a bubble, it means that our Beacon target will be even safer while we heal the rest of the group. It will also increase the potency of our AoE heals, although it remains to be seen how powerful Healing Hands is in practice.
The key to this mastery bonus' success or failure is in the stacking. If each of our heals replace a previous bubble, then it's possible we'll run into the issue where we heal twice between boss swings, yet only one heal's worth of shield is active. If each of our heals stack into a single, powerful shield, it's would allow us to use tactics like unloading our cooldowns early to give the tank a massive absorption shield to survive some brutal attack. Divine Aegis, the discipline priest talent, currently allows for the absorption effects to stack, so I hope Blizzard continues along that train of thought for our mastery bonus.
Preventive healing rounds out the class
Blizzard wants every healing class to be somewhat capable of playing any healing role. Druids and priests should be able to heal the tanks and paladins and shamans should be able to heal the raid. The spells that each class has gained in Cataclysm clearly show that paradigm being enforced. However, there aren't two sides to healing, but rather there are three. Healing the tank requires powerful single-target healing, healing the raid requires multi-target heals, and preventative healing requires HoTs or absorption effects that can be leveraged ahead of time. Preventative healing also adds more skill and strategy to healing, as we have to make decisions about spell usage before anyone actually takes damage.
With the removal of Sacred Shield, we also lost the Flash of Light HoT effect from Infusion of Light. Absorption effects will effectively be our only preventative heal, and so ensuring that they're powerful enough for us to get the job done will be incredibly important. Just look at the heroic Lich King encounter-discipline priests are simply irreplaceable. Holy paladins can try to stand in their shoes, but we simply had no way to prepare 25 people to be hit by a powerful attack outside of cooldowns. Giving us a way to proactively heal our group could be the last piece needed in making holy paladins the complete healing package.
The Light and How to Swing It (Holy Edition) helps holy paladins become the powerful healers we're destined to be. Learn the ropes in Holy 101. We can help you keep a tank alive, heal a raid when necessary and beat the global cooldown. Tanking is a job, DPS is a craft -- but healing is truly an art.