Healing Through: Halls of Reflection

This is the first post of a series I'm starting and will try to update regularly. Healing Through will compile my healing guides for instances and raid bosses. I'll try to target everything that I found hard, or when I have nice tips to give.
Healing Through will mostly be healing through an event as a paladin. I hope the tips can help other healers, I'll perhaps extend it to Discipline Priest and Druid if I find some time ^^

Healing Through: Halls of Reflection Heroic (and Normal)

After a few experiences in Halls of Reflection as a healer (3 times normal, 2 times heroic) and discussing it with a friend who did it as a dps and healer, I think this instance is going to be the next nightmare of healers (5-Man wise).
I guess some of you that tried it on heroic know what I mean. I'm going to try to point out the difficulties and what to expect/do during the different parts of this instance.

Pro-tip: during the whole instance all mobs are undead, don't forget Holy Wrath, it stuns mobs for a few seconds, can prevent a wipe, especially if your tank needs 2s to pick-up a group of mobs.

Pro-tip: Cleanse is mandatory (seriously :p) during most of the instance, so don't go into Halls of Reflection without an add-on to help you like Decursive (up-to-date on curse add-ons website).

Phase 1: The Gauntlet

The instance starts with waves of ghosts attacking you, several at a time. You have to defeat 5 waves to get the first boss, 5 more for the second boss and then you go to see the Lich King.

I think these 10 waves are the hardest part of the instance for the healer. The reason is the random aggro, the fact that your tank will have a very hard time maintaining (or even gaining) aggo on the casters/distance mobs, and the sheer amount of heal you'll have to do to keep the aggroed dpsers alive (and you).
To say things simply, don't try HoR heroic if your tank is not good at gaining aggro and keeping it on several targets at a time. A tank able to silence caster opponents is the best. I think paladin tanks shine in this instance.

How to not turn crazy during the gauntlet?
If you do it "the basic way" and your group stays in the middle of the room, it'll be hard. It can work in normal (I did it like that) but it'll certainly not work in heroic. The reason is that the ghosts will aggro the closest person, damage you or your dpsers (squishy) resulting in you healing a lot, taking aggro from several mobs and being ganked to death in like 2s.
The solution is to use "line of sight" to force the mobs, and even the casters/distance to get to your group and especially come in reach of your tank. For that you have two choices.

Positioning your group.
You can try to stay in the entrance corridor, it'll still require your tank to go out and pick-up the casters, or you to heal him get aggro and go from left to right of the corridor to use line of sight and force all distance mobs to come towards your tank (who should be between them and you).
The other solution is to hide in one of the alcoves on the side, where the two first boss ghosts are. You can have everyone hide in the side of the alcove, wait for the mobs to come, and your tank just has to pick-them up right here. It's the easiest way, just look-out for aoe casters that hurt!

What else do you have to expect?
First several mobs have debuffs, and your party will be debuffed a lot (magic/poison I'm sure, I don't know about curses they are not displayed on my decursive). It's hard to cleanse & heal all the time, I advise you to leave the debuffs and concentrate on healing when anyone goes low.
Pro-tip: *always* keep your Beacon of Light on your tank at all times, even a few seconds without healing can result in a dead tank in heroic.
Now there is a very very nasty debuff, rogue ghosts use a poison that reduces healing by 50%, if you leave that on your tank he'll die very fast even with a Beacon. So you have to cleanse the tank at all time, if you let several debuffs on him, when he'll get the poison it could require you 3 or 4 gcds to cleanse remove it, and he'll be dead by then ...
Now last but not least, the healing aggro. Ok you forgot it even existed, it'll be reminded to you the hard way here. If you use one of the los positioning techniques, the mobs will all come towards your group. It's perfect if your tank can pick-up all of them before you have to heal, but it will rarely be the case, as they won't reach your group at the exact same time. If you have to heal him before all the mobs reach your group (very probable) then you'll have the aggro when they come close. And the aggro of 3 mobs in heroic will get you "dead in 2s". In the end your life is in the hands of your tank, if he's fast and able to pick-up the mobs before they reach you you'll live, if not you'll die on each wave ... I experienced the "rez" each 2mn with a bad tank, and I swear I'll not pug that instance again XD
Pro-tip: paladin consecration is the hottest thing ever invented to protect a healer, and don't forget to use Divine Protection, Hand of Protection ...etc on yourself.

Boss 1: Falric

Now if you can manage the waves you'll be able to face the bosses. Rejoice, they are way way easier than the waves, from a healer perspective. They still hit hard and require reactive cleansing though.

Falric is the first boss, he has two nasty abilities:
Impending Despair - Causes Despair Stricken, stunning the target for 6 seconds, if not removed after 6 seconds. Magic effect.
Defiling Horror - Inflicts 2,500 (4,000 in heroic) Shadow damage every 1 second for 4 seconds.

Impending Despair only requires a cleanse, but don't forget it, if your tank or you get stunned 6s, you're asking for a wipe.

Now, and especially as a paladin without any hot or proactive healing like shields, Defiling Horror is the worse part of this boss. Every 20s or so, Falric will fear your whole group and deal strong shadow damage on everyone.
Pro-tip: remember to switch to shadow protection aura when he engages.
Your whole party will be hit for 10K (16K in heroic) shadow damage while you can't heal. If they are not full-life they could be dead before you get out of fear. And the boss then immediately resumes hitting your tank who will have suffered the same shadow damage as everyone. You then have 20s to heal everyone to full again before the next fear.
The "easy" way to survive this fight is to be sure that your tank will have a Beacon of Light when the fear ends and start casting Holy Light on your whole group one after the other. One Holy Light should be enough on each member, perhaps with a Flash of Light in heroic. If your tank is a little low at the end of the fear, start with a Holy Shock on yourself.
Pro-tip: if at any time someone goes too low during a fear, bubble and heal.

All in all Falric isn't very hard once you get the timing right.

Boss 2: Marwyn

Marwyn is the last step to be rid of the waves, so you don't want to wipe on him :P
Happily he's not very hard, even easier than Falric is you don't miss on your cleanses.

Marwyn three main abilities are:
Obliterate - Inflicts 18K (26K in heroic) Physical damage, mitigated by armor.
Shared Suffering - Inflicts 4K (6K in heroic) Shadow damage every 3 seconds for 12 seconds. If dispelled, splits the remaining damage equally between all players. Magic effect.
Corrupted Flesh - Reduces maximum health by 25% (50% in heroic) for 8 seconds.

There is a little "trick" here. If you don't cleanse the Corrupted Flesh on your tank, he could die of an Obliterate is you don't keep him full life (most tanks will be reduced to around 20K life by a Corrupted Flesh on heroic difficulty. So you have to cleanse. But there is Shared Suffering that will do about 5K damage to everyone in the group if you're fast on cleansing it.
What should you do in the end? Well, the answer is relatively easy, only cleanse your tank at all times. It could result in group damage, but as long as everyone is topped that won't be a killer. That implies you'll have to heal the target of Shared Suffering but with a Beacon of Light on your tank, this won't be a problem, healing two people at once is easy for a paladin even without hots.

As a side-note Marwyn also lands shadow zones under you from time to time, who's not used to that now, just move away (yes you too Mr.Tank ^^).

Phase 2: The Running Away from the Lich King

Now you'll killed Marwyn. Good job, you can have fun running with the Lich King and Frostmourne right behind you.
This phase is much easier for you as a healer, just be cautious that the abominations have a cleave and a frontal aoe, so stay on the sides and out of direct contact if you can. Your dpsers could get hit from time to time be quick on the heals and keep an eye for a saving Hand of Protection.

This part of the fight is much more focused on the dpsers, exactly as the first part of the instance is hard on the tank and healer.
Your dpsers have to be able to down all the mobs of a wave before the Lich King reaches you, it could seem easy during the first two waves, it's surely not as easy on waves 3 and 4.
Now, the mobs are not arriving exactly at the same time, and if any dps (or you) get the aggro on an abomination and your tank doesn't pick-it-up in time, you'll have a corpse on the ground (they nearly OS any non tank character). These big flesh puppets also cleave and have a frontal aoe ... so if the dpsers are the ones in charge of the success, your tank still needs to be very quick and aware.
Be happy, this phase should really not be so hard on you compared to the gauntlet, but it doesn't mean it'll be easier for your group.
Pro-tip: try to help your dpsers if you have some free time, paladins do have good dps abilities on undeads. Especially always use Holy Wrath as soon as it's out of cooldown and don't fear to use consecration as soon as your tank got aggro on a whole pack.

You're done?
Enjoy the cut-scene, you deserve it, especially in heroic (with good gear the normal difficulty should not pause you any problem).

See you soon for more Healing Through series.

note: There is a nice article on WoW.com about the perspective of a tank during HoR, and I think what he says about it is right on the spot and will give you an idea of all what a good tank has to do during that instance gauntlet.