DPS classes love fights that are simple enough that they can focus on running their rotation optimally. It lets them stretch their legs and see how much damage they're truly capable of. Patchwerk is always the golden example of this style. Rogues, mages, and the rest didn't have anything to worry about except their own personal DPS. Fight mechanics only get in the way of a damage dealer doing his job. Every patch of fire or Whirlwind only serves to make him perform suboptimally.
Healer-oriented encounters are the complete opposite. Instead of business as usual, healers are challenged to break out of their comfort zone and do things they've never done before. Casting DPS spells at Loatheb while his terrible aura persisted. Watching health bars glitter in the red as Leeching Swarm turned our own heals against us. Gathering orbs midair as we tried to save a dying dragon with our amazing throughput. Now, in Blackwing Descent, we are faced with yet another terrible foe: Chimaeron mixes elements from all of these fights to give us a truly unique healing experience.
While I'm not going to spell out the entire fight here, you will need to know about a few key abilities. The first is Massacre, which will instantly kill everyone in the room. Luckily for us, we have the aid of the Bile-O-Tron 800, which prevents us from dying if we have over 10,000 HP when an attack comes in. Chimaeron hits so hard that there's no difference between having 10k life and 50k life, as we're reduced to 1 HP by Finkle's Mixture anyway.
The Massacre / Finkle's Mixture mechanic is very similar to Anub'Arak's Leeching Swarm, which encouraged us to keep the life of our raiders low. We only want to heal for just enough to keep them alive. Considering that most raiders have at least 100,000 HP once buffed, I try to shoot for keeping everyone at 10% life. If players are hit by Massacre when they're under 10,000 HP, they die instantly. Keeping all of your raiders above 10%, but only just above, is the best way to preserve your mana during this encounter. I like to use Light of Dawn directly after a Massacre to help boost everyone's life quickly, although it only does part of the job.
React fast to Caustic Slime
Chimaeron will also randomly shoot raid members with Caustic Slime, causing their life to plummet to 1 HP. It's critical that these players are brought back to 10k life immediately, or they risk dying during a Massacre or follow-up Caustic Slime. Use Holy Shock and Word of Glory to accomplish this quickly. I actually picked up the Last Word talent to help while learning this fight, as players will nearly always be below 35% life. You need to be quick to react to a players hit by Caustic Slime, so work with your other healers to coordinate this effort. Again, you only want to heal them to just over 10k life and then stop healing, conserving mana. Don't bother with a Flash of Light or Divine Light, as they'll only overheal.
Double Attack and your tank
So the raid will be taking random damage, and you'll be healing them up quickly to 10k life. The main tank will go through a similar process, during which the boss will hit him for massive damage due to Break. The Bile-O-Tron keeps the tank alive through Chimaeron's swings too, and so the same 10% rule applies. I like to put my Beacon on the main tank, as between the Beacon heals and the Protector of the Innocent heal transfers, I can usually keep him above 10% at all times. Have the other healers in the raid assist by tossing their HoTs onto the tank as well.
Now, what happens if you're hit twice by Chimaeron, before you can be brought back up over 10k life? Typically, it means that you're dead. Chimaeron has a move specifically designed to kill your tank, Double Attack, that causes him to swing twice. The main tank will have several stacks of Break on him, increasing damage taken. If both Double Attack blows land, your tank is toast. The solution to this is to have a second tank Taunt the boss, absorb the two blows, and then have the main tank take over. The second tank needs to have enough life to survive two blows from Chimaeron, and so we'll actually spend quite a bit of time healing the second tank until his health bar is full. It's sort of an awkward idea, as we let the main tank's life dwindle while healing the off tank to full, but that's how it works.
Feud is the ultimate throughput test
At this point, we're using our instant and cheap heals to quickly heal up victims of Caustic Slime and keeping our off tank topped off. Since we only have to really do any serious healing to one target, our mana usage is actually relatively low. Feud is then introduced to truly stretch our throughput and mana to their limits. If you spend your mana poorly during the rest of the fight, you'll find yourself OOM when Feud lands. Managing your mana between the phases is one of the most important aspects of the encounter.
Feud causes Chimaeron to stop hitting our tanks but also knocks the Bile-O-Tron offline. Since we don't have Finkle's Mixture, incoming attacks can actually kill us. On top of that, Chimaeron will Massacre everyone right before he starts Feud, and so everyone will go into this phase with only 1 HP. Chimaeron will cast three Caustic Slimes on the raid during Feud, and it's up to the healers to do enough healing to keep everyone alive. Caustic Slime splits its damage between nearby players, so everyone will be stacked up to be healed. What's the best ability when the raid is stacked? Holy Radiance, of course.
Holy Radiance will be up for every Feud phase, and you'll be using it to help bring the group's life bars up quickly. I suggest using Divine Favor right before Holy Radiance, as the bonus haste will typically allow you to get a few extra ticks of Holy Radiance off during its duration, and the extra critical strike change can't hurt. I like to use the DF + HR combo for the first Feud, and then I use my Guardian of the Ancient Kings to splash healing to the raid on the second Feud. You should also have 3 Holy Power points saved up going into Feud, so that you can instantly use Light of Dawn. Finally, you need to pick a powerful heal to top everyone off during Feud. Flash of Light is great for 25-man raids, while I can usually get away with the cheaper Divine Light on the 10-man version.
During Feud, Chimaeron will only cast three Caustic Slimes. Each CS hits for roughly 40% of any given player's HP, and so everyone needs to be above 40% before the next CS lands. The total damage done to each player will be around 120% of their total life, and we can use this knowledge to save ourselves some mana. If the first CS has hit the raid, and we've subsequently topped everyone off to 90% or more HP, we can stop healing. Both of the next Caustic Slime attacks won't kill anyone, so we can start saving mana. I typically use Divine Plea once everyone in safe during the Feud phase. Because we know exactly how many times we're hit with CS, we don't need to continue healing. Note that immediately following the final CS, Chimaeron will cast Massacre, bringing everyone to 1 HP. This further reinforces the idea that any extra healing that we do during Feud is wasted.
Time to die
Once we've reduced Chimaeron to 25% life, he'll spread a Mortality debuff on the raid and himself. It makes the boss immune to Taunt, although he'll also take 10% more damage. Additionally, it reduces all healing taken by 99%. It's impossible to try to heal anyone during this phase, and so we get to switch to shockadin mode and start casting Exorcism to add some DPS. Your mana pool will empty quickly without Denounce, but that's to be expected. Just add as much damage as you can, and if you're targeted by the boss, try to kite him for as long as possible. People are going to die during this phase, and it's all about buying enough time for your DPS to finish him off. Don't bother using your Divine Shield, as this will cause Chimaeron to target someone else, and we want him killing us first. Our DPS is weak when compared to a tank or DPSer, and we can buy them time as Chimaeron works on wrecking us.
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.