Details of mastery stacking
Other than their new stacking effect, our bubble mechanics haven't changed at all. Each eligible heal we cast refreshes the bubble duration, and only our direct heals can proc the bubbles at all. The maximum bubble size is based off of our total health, which means their total size should scale as we are raid buffed and acquire new gear. I'm personally sitting on about 120k life without any buffs, meaning my master bubbles can grow to 40k total absorption. That's over 10 times stronger than my individual mastery bubbles, considering my low mastery rating.
When talking about the effect of this change, it's important to note that it's not as simple as a straight buff to mastery. If the tank that we're healing is taking damage quickly, especially when tanking multiple mobs, then there's no real change. Mastery's stacking effect is only valuable if the bubble actually gets a chance to build up, which isn't always the case. The stacking effect will be very valuable on fights where the tank takes damage in slower intervals, as we'll have time to cast multiple heals on the tank before the next swing arrives. I'm looking specifically at fights like Chimaeron, where we're tasked with filling a tank's empty health pool in just a few seconds. Each heal builds the bubble a little bigger, giving the tank a much bigger effective health pool once he starts getting beat on.
It's not a cure-all
A large number of holy paladins in the community have been advocating for stacking mastery bubbles since its introduction. While I agree that allowing our mastery bonus to stack is a step in the right direction, it also doesn't fix all of the problems with our mastery as a whole. Haste has been our go-to stat for one major reason: It affects Holy Radiance and Beacon of Light. These two abilities make up a large part of our total healing done, and having them ignore mastery only weakens its value.
Holy Radiance, while only just introduced in Cataclysm, has quickly become one of our signature spells. There's no AOE challenge that we can't conquer with Holy Radiance. Without it, we really don't have any AOE healing options outside of the lackluster Light of Dawn. Haste affects Holy Radiance in a very powerful way, giving it extra ticks that significantly boost its healing capacity. Haste also improves the HPS of all of our casted healing spells as well, making it the most potent secondary stat.
Beacon of Light has been our spec-defining ability since its introduction. While we've seen it rebalanced several times during its lifetime, it has always ended up being a core ability to the holy paladin style of play. Mastery bubbles don't appear on our Beacon of Light target when we heal someone else. Since our Beaconed target is most likely taking regular damage, bubbles would be incredibly effective if placed on them. With patch 4.2 allowing our Holy Lights to transfer 100% of their healing done to our Beacon target, we are going to be spending more time healing off-Beacon than ever before. The patch notes are bad news for mastery, which favors direct healing over all else.
Mastery is a tank healer's stat. If you're tasked to heal a tank who gets hit infrequently but for massive damage, then you really can't go wrong with mastery rating. I'm already imagining how much this could help with heroic Maloriak's Black Phases, where we have to squeeze a lot of healing onto the tank into a very tiny window. On a more typical raid encounter, the tank is likely getting hit between each one of our casts anyway. In heroic dungeons, tanks are usually handling multiple mobs, and so our mastery bubbles were almost completely effective anyway.
Holy Radiance's tentative balance
Until mastery affects Holy Radiance and/or Beacon of Light, it's simply always going to be considered a tertiary stat. A stat can't ignore two of our biggest sources of healing and expect to be competitive. Haste affects all of our spells, even including our non-heals via the GCD reduction. With reforging allowing us to customize our gear, we can basically pick our two favorite stats and aim to maximize them both. In order to break up the haste/spirit lockdown, mastery and crit are going to have to see a significant change. Stacking mastery bubbles is a step in the right direction, but it doesn't yet tip the scales.
The Light and How to Swing It: Holy helps holy paladins become the powerful healers we're destined to be. Learn the ropes in Cataclysm 101 for holy paladins, study the new balance between intellect and spirit and learn how to level your new Sunwalker. Tanking is a job, DPS is a craft -- but healing is truly an art.