Teron Gorefiend Tactics

Preparation

Only one single tank is needed, all other tanks should switch to DPS or Healing gear. The Gorefiend tank has to deal with solid melee damage. The usual mix of damage dealers and healers (6-8) is reasonable for this fight.

The whole raid needs the Shadow Protection buff. Cauldron of Major Shadow Protection is also really useful. It's possible to wear some extra shadow resistance, but not much - it's a DPS race, not a battle for survival. Soulstones should be created pre-fight, but not pre-cast. They are needed for healers getting Shadow of Death.

Teron can be tanked right where he stands, and ranged DPS should group behind the MT opposite to the entrance. This gives the whole length of the room for the Ghost form players to kill the Shadowy Constructs.

Teron Gorefiend

Teron himself has a relatively low amount of health and must be killed as quickly as possible. It's fairly standard tank and spank, he's not tauntable, but a good tank can control him rather easily. As usual, melee DPS must stand behind him to avoid increasing his attack speed by parries. 3-4 healers should be able to keep the tank up, the other healers should take care of the massive damage the raid takes (this is another fight where Chain Heal and Circle of Healing are very effective).

Incinerate (the fire dot) must be dispelled as soon as possible, two Priests or Paladin dispellers should be predesignated.

All damage enhancing, long-cooldown abilities like Bloodlust (or Heroism) should be used as early as possbile after the tank has settled into an initial threat lead.

Shadow of Death

Every 30 seconds, a random raid member (not the person with aggro) receives this debuff. After 55 seconds, the debuff turns the player into a Ghost and spawns four Shadowy Constructs. The Constructs attack the raid, and usually cause a wipe if they succeed. Therefore, the Ghost player must kill them before they reach the raid, by kiting and nuking them with the Ghost abilities.

After the 60 seconds ghost phase, the player simply dies. Healers (ex. Shamans with an available Ankh) should get a Soulstone when they receive the debuff, so that they can resurrect at this point.

About 15-20 seconds before the debuff runs out, the affected raid member must move to the south end (as far away from the raid as possible). The first action after turning into a Ghost should be to AoE damage the Constructs with Spirit Volley (key '5'), move with the group and then AoE freeze them with Spirit Chains (key '4') as soon as the GCD allows. During the 15 sec cooldown, the Constructs must be nuked with Spirit Lance (key '3'), which damages and slows a single Construct.

This is the most difficult phase for the Ghost player - while slowly moving backwards towards the raid, all four constructs must be hit with Spirit Lance in turn to keep them all slowed and close together. Each Spirit Lance should hit a different target (either using the Tab key or mouse for targeting in a rotation). After 15 seconds, a second combination of Volley ('5') and Chains ('4') is available, after that the Constructs should have taken enough damage to die with 2-3 more Spirit Lances.

After the four Constructs are dead, it is a good idea to look for Constructs from the next player, and help kill them. If no Constructs are up, it's possible to move to the raid and buff a healer with Spirit Shield ('7'), and then get within melee range of Teron and attack him with Spirit Strike ('1').

Since learning the Kite'n'Nuke technique required for killing the Constructs may be difficult for classes which normally do not kite, and learning it under raid conditions is rather expensive (one wipe per try), it's a good idea if all raid members practice using the Teron Gorefiend's Shadowy Construct simulator before attempting him. The simulator is not a replacement for the real thing, but it gives players the general idea what to expect.

Do not try to exploit this encounter by disconnecting or hearthing out. Doing so immediately spawns the constructs with no friendly ghost to kill them. That is a wipe.

Notes

Players with the debuff should not die by any other cause while still fighting Gorefiend, because in that case the Constructs spawn directly in the raid, and this frequently starts a wipe
If someone is slow in killing the constructs, the next person with the debuff may draw aggro from a construct while on the way to the back of the room. Healers must be aware of this possibility and keep the running player up
If there are any problems (like high latency or slow reaction time), it's better to skip the first Spirit Volley. The safest approach in that case is to spam '4' for the last seconds before the debuff runs out, to make sure the Constructs are frozen
For the tank it's tank & spank and because he hits fairly hard, Gorefiend is usually regarded as an excellent encounter to test threat techniques and maximizing it.

Ghost controls

Some UI mods can lead to the Ghost form ability controls to appear at an unexpected location (or even not at all). When preparing for this encounter and using an action bar mod, it's a good idea to test whether the ghost controls are visible. The cheapest method to test this is the Battered Steam Tonk Controller, or a Steam Tonk Controller crafted by an engineer.

Bartender, Bongos3, Dominoes all have an extra action bar called 'posses' bar, which is used when the player takes direct control over another entity. Players should configure their mod so that this bar is visible.

Avoiding Shadow of Death

Classes which can remove themselves from combat can completely avoid Shadow of Death. By using Vanish, Feign Death, Divine Shield or Ice Block during the cast time of Shadow of Death, players avoid getting the debuff, and Teron does not cast it again until 30 seconds later.

The ability must be used during the 1 second cast time. Teron regularly targets random players to use one of his abilities, but Shadow of Death is his only ability with a cast time. The targeted player needs to react very quickly, to faciliate this a macro like

/stopcasting /cast <ability name>

may be useful.

If players with these abilities do manage to avoid Shadow of Death, the raid effectively saves one entire Shadowy Construct cycle, which is a big boon.