Illidari Council Strategy

Preparation

1 main tank (Gathios)
2 off-tanks (Malande and Veras)
1 mage tank (Zerevor)
12-13 damage dealers
8-9 healers

All raid members must have at least 11k HP buffed. A rogue wearing Gladiator's Leather Gloves is extremely useful (for the ranged physical spell interrupt).

The Pull

Similar to High King Maulgar, a correct pull is difficult to set up, but extremely important. In order of precedence, the mobs should be assigned as follows:

A mage buffed with Hand of Protection, a full stack of HoTs and a Power Word: Shield starts the fight by pulling Zerevor (the mage) from 35 yards away, towards the left side of the platform
Gathios (the Paladin) should be immediately misdirected to the main tank, and tanked on the opposite (right) side of the platform
Veras and Malande can both be tanked by one off-tank each near the middle of the stairs, about 15 yards apart. Additional misdirections facilitate this pulling

Gnomes can experience line of sight issues when attempting the pull. They need to either go to the top of the platform or change their character model (e.g. with [Noggenfogger Elixir] or [Savory Deviate Delight]).

Pet Pull

The critical element is the mage, who may easily die if one of the other bosses attacks him. It's possible to start the fight with an Imp (or other pet), which then takes the first Arcane Bolt. This gives the raid a second or so to get the mobs under control. Of course, the mage tank must give the pet just a split second head start, and gain Aggro on Zerevor (and spellsteal) as quickly as possible.

Tanking

Lady Malandes heals must be interrupted under all circumstances, and all her other spells should be interrupted as much as possible. Since she's the preferred target of Gathios' blessings, she's invulnerable to one type of damage (physical or magic) most of the time. Therefore a total of four interrupters should stay on her - two physical and two magical. Curse of Tongues, Deathfrost and Mind Numbing Poison are highly recommended. If there's some AoE on her spot and she's blessed vs. magic, a last resort is to have a Rogue wearing the PvP gloves interrupt her by throwing. The group tanking/interrupting her must call out the target if a Divine Wrath gets through, so that the raid healers can adjust.

High Nethermancer Zerevors Dampen Magic must be spellstolen as frequently as possible. Everybody must keep at least 10 yards away from him to avoid arcane explosion.

Gathios the Shatterer is the main DPS target. The main tank should use spell reflect when the Seal of Command is Judged (this happens in regular intervals). The melee damage dealers must be extra careful never to attack him from the front, since an increase of his attack speed (after a parry) can mean near-instant death for the MT. This is particularly difficult, because if there's some AoE taking place, the tank has to move. The best practice is to stop melee until Gathios stands still in his new location.

Aggro (on Gathios) is not an issue, because the spell reflects create a lot of threat. After the second reflected Judgement, all damage dealers can safely ignore their threat meters and go all-out.

After a Vanish, Veras temporarily ignores his aggro list, until he's hit again by the tank. A druid or paladin tank is therefore better suited for this task than a warrior. If a warrior must tank him, it's highly advisable to set up an macro which follows an Intercept or Intervene directly with an Autoattack.

Healing

Two healers on the main tank, one on each of the three other tanks, remaining healers on raid heal. The whole raid has to watch out for a lot of different AoE effects. There's about six different types of AoE and debuffs which can occur, and there is nothing predictable. Raid members must be very quick to run out of AoEs, and healers must be extremely alert to heal through some poison debuff or other damage, while evading AoEs themselves.

Tips

One tactic that can help your tank locate Veras Darkshadow after a vanish is to have a hunter make the a spamable macro to mark Veras before he reappears. This should put a big red arrow over Veras about 3 seconds before he reappears.

/focus Veras Darkshadow /cast [target=focus, exists] Hunter's Mark