Tactics: Shade of Aran

Strategy
The problem in this fight is that the whole raid must learn to avoid damage. The Shade of Arans basic attacks are not very dangerous, but the special attacks are deadly. Each raid member must pay attention which attack is upcoming, nobody can sit back and just do their usual routine. Once everybody learns how to move (or when not to move), the fight actually becomes rather easy.

In order to avoid the Magnetic Pull/Arcane Explosion everybody must run to the outer wall of the room, the Blizzard forces people towards the center (or the other side of the room), and Flame Wreath inhibits movement. Beyond this, casters want to stay outside the AoE silence and classes with spell interrupt abilities want to concentrate on what he's casting.

The encounter cannot be reset.

Gear
Aggro is of almost no relevance, because Aran chooses his targets semi-randomly, thus the tanks should put on DPS gear. If the raid choses not to interrupt arcane missiles, some arcane resistance can be useful. Everyone in the group should strive for at least 8k HP after buffs, more is better. Even healers and ranged DPS must be able to survive a wave of arcane missiles (7k), and everybody must be able to survive the pyroblast (7.5k).

Interrupts
The raid should agree on a general strategy — it is either possible to have Aran conserve his mana (so that the polymorph/pyroblast perhaps doesn't occur), or to have him burn it quickly, so that the polymorph clearly occurs before the water elementals. If the raid doesn't have a very large and adept amount of interrupts, the usual procedure is to keep two schools locked out, and allow him to freely cast the third one.

If Aran is supposed to conserve mana, it is recommended to interrupt and lock out Fireball and Frostbolt, and let him freely cast Arcane Missiles. If he should burn his mana quickly, it's better to lock Frostbolt and Arcane Missile, and let the Fireballs uninterrupted.

Interrupts on Fireballs and Frostbolts should occur near the end of their casting time, because he expends mana only at the end of the cast and he will be doing nothing else for nearly 2s. Arcane Missiles should be interrupted early, as he spends the mana upfront and thus they will cause less damage.

It is useful to assign each player with an interrupt ability one type of spell which he should take care of, this avoids everybody interrupting the same spell, and then have the abilities on cooldown for the next one.

It should be noted that Feral Druids CAN use Feral Charge to interrupt any of Aran's three schools. It will still interrupt his spells even though he is immune to the snare.

Blizzard
This special attack will materialize as a blue, translucent cloud on the floor that slowly moves clock-wise along the outer perimeter of the room until it has completed a whole 360° turn and disappears again once it reaches its point of origin. The cloud will snare any player it touches and is trailed by a damaging AoE blizzard which will extend backwards up to 180° of the blizzards' path.

Players in melee range to Aran do not have to worry about the blizzard as it will only affect the outer radius of the room. Ranged fighters and healers should always keep a lookout for the cloud and run away clock-wise from it (but avoid running into the tail of the blizzard) unless they are already affected by the snare, in wich case they should immediately turn to cross through the safe center of the room. This will likely expose them to Aran's silencing counterspell, but is still the lesser of two evils. If you keep your raid evenly spread out in the room (in particular the healers), this should not be a serious problem.

Flame Wreath
If Flame Wreath is upcoming, the whole raid must immediately stop moving, simple as that. People must wait until the auras are clearly visible, and may only move again when they are sure they will in no way come near one of them.

The effect is triggered in particular by the following:
All forms of player movement, including jumping, sitting down, standing up or turning
Paladins' Divine Shield
Rogues Cloak of Shadows
Accepting a resurrection (Rebirth or Soulstone)
Mages' Blink
Druids' shapeshifting

The following will not trigger the effect:
Spell casting
Movement resulting from a spell cast (like Mind Flay)
Nether Protection
Pets
Magnetic Pull / Arcane Explosion
Prior to this, Aran will always cast an AoE slow. If everybody starts immediately running right after the magnetic pull (no turning around, just run!), even slowed people can reach the wall before the explosion. The slow can be broken by PvP trinkets, Rogues' Cloak of Shadows or Improved Sprint, Druids' Shapeshift, Warlocks' Spellstone, Paladins' Blessing of Freedom, and Gnomes' Escape Artist. Aspect of Cheetah/Pack will also help. Mages can blink to an edge and use the extra time for an evocate. Priests and Paladins should keep an eye out for slow reactions (or anyone in "Chains of Ice"), since the slowing effects can be dispelled. Warriors can use Intervene to quickly charge up to a raid member at the edge of the room.

Water Elementals
A Warlock is invaluable here, because the Water Elementals can be banished and feared, and are susceptible to Curse of Tongues. The adds should be tanked and nuked ASAP. It helps a lot if the tank wears frost resistance gear. The elementals have roughly 13k HP as of the newest patch, so they can be burned down very easily. Because of this, having a warlock in the group is not as important as before.

Nevertheless, the spawning of the Elementals can become a problem when happening simultaneously with a special attack of Aran where everyone is too distracted to immediately grab the aggro of an Elemental before healing aggro draws their combined fire on a poor healer. This is exactly the one moment in this battle you want to save up any defensive or offensive special abilities or trinkets with cool down up for.

Regenerate Mana
If the raids DPS are high enough, and the interrupts work well, this phase does not necessarily occur. If it does occur, the healers have to be on their toes to very quickly heal the raid after the Pyroblast (preferably using AoE heals). The polymorph breaks a very short time before the pyroblast, so it is possible to cast some protections (Priest shield, HoTs, Paladin bubble, Mage fire ward, fire resistance totems etc.) right before the Pyroblast. After the blast, raid members should use health potions and Healthstones to heal quickly.

This polymorph will even work on characters which are normally immune to polymorph. Druids in Tree of Life form are not considered a valid target for the polymorph however. Therefore, a raid can have the druid cast Lifebloom or another HoT on as many people as he can in anticipation of the AoE Pyroblast. Preparing the raid member with the lowest HP who is not in the druids group to receive Swiftmend would also be an option, as well as preparing Nature's Swiftness to cast either Rebirth (if needed) or Healing Touch.

A big problem associated with the polymorph/pyroblast is that it frequently occurs close to the summoning of the water elementals. This must be avoided, because the water elementals are deadly right after the Pyroblast. DPS needs to slow down or speed up if it appears they are likely to happen close together.

Druids may now use Barkskin to reduce the damage dealt to them by the Pyroblast, which for druid healers may be essential in keeping themselves alive. Then cast Tranquility right after the Pyroblast to quickly heal up your half of the raid to full health again