Zorn and Toth

I have found a nice guide for Hard Mode Zorn and Toth. It supports the idea I had about the DPS/Healers standing on the other side of the valley, which makes it easier for healers to stay out of the other group's target's AOE while still keeping in range of the tank (I.E. what often happened that while the tank and Zorn were just under 30 metres away, Toth was in fact closer that 25 metres thus doing damage which can be avoided).
Also the tanks should try to stand closer to healers than the bosses are, this is quite difficult and only possible after the initial positioning but due to the shape of the valley, the healers can position themselves to achieve the same effect (see the video).
It is also suggested that it is the tanks that change places rather than exchanging the bosses' places. This help to keep the position constant, limiting the problem I pointed out earlier.
The Jump together/tank swap phase occurs at about 85% 65% 45% and 25% and 5%. The First boss to get to that HP threshold triggers the jump. The people attacking Zorn should be wary of this and not use dots as the fearful debuff is applied during Toth's jump. Procing damage relics should also not be used for this fight.

It also suggest for the whole groups to swap targets in order to prevent being damaged from the 'Fearful' debuff.

If even then we keep failing, it is possible to 3 heal the fight and still avoid the enrage.

http://mmo-mechanics.com/swtor/forums/Thread-EC-Zorn-and-Toth-Hard-Mode

Firebrand and Stormcaller

For F&S the only change is that the shields with Trandoshans will spawn in different locations. It is also very helpful to have a ranged DPS off the tank to kite the plasma arcs and cleanse their own targeting beam. As such there is some loss of DPS but it should not be a massive issue. It is also suggested that Tanks swap due to Incinerate and DD doing much more damage but with our current tactics this should not be an issue (especially if sage is on Firebrand to Force Armour the tank during Incinerate).

Colonel Vorgath

Imperial Demolitions Droid (the one that is scanned for and drops the defusal kit) Must be interrupted, his cleave has massive damage and he also has and AOE knock back which will likely knock the group into the active mines.
While killing the aforementioned droid, two Imperial Assassin Droids will spawn, these must be CC'd and killed one by one after the main droid is dead, otherwise they do massive AOE damage (suicide bomb essentially). One strategy is to have the tank run into one to take all the damage but killing them with ranged is preferable.
Once the minefield is solved the only change is that the turrets are not CC-able and as such must be tanked by one tank while the other 1 tank Vorgath. The turrets will automatically hit the player closes to them. Positioning should as follows:

M M M M <----- Mines
M M M M
M M M M

T T
T T <------- Turrets near vorgath
TT <----- Turret Tank
B <------- Boss
BT <------ Boss Tank
ML <------- Melee
R/H <------- Ranged/Healers

Kephess
3 groups of Shielded Trandoshans spawn very soon after each other perhaps requiring an OT for the third group if the first 1 is still up.
ATAT should be killed in 3 attempts.
Kephess will cast 'Touch of the Masters' (debuf) when he knocks back the tank and proceeds to cast 'Breath of the Masters. If he is not taunted by the other tank before he finishes casting, he hits the original tank for 25k

Hard Mode Drops

Toth and Zorn: Campaign Legs, Campaign Bracers, Random Black Hole gear or Campaign Relic
Stormcaller and Firebrand: Campaign Belt, Campaign Offhand, Random Black Hole MK2/MK3 gear or Campaign Relic
Colonel Vorgath: Campaign Chest, Campaign Gloves, Random Black Hole MK2/MK3 gear or Campaign Relic
Warload Kephess: Campaign Mainhand, Campaign Helm, Random Black Hole MK2/MK3 gear or Campaign Relic

If you have no Shadow tank then the tank swap on Firebrand + Stromcaller isn't that hard, might be useful to do it anyways.

All our tanks are vanguards so it would be pretty easy just to taunt and storm.

Zorn and Toth:
I've also seen guides showing the tanks positioning the bosses at the back of the canyon, but I like this positioning better. It gives the tanks a chance to build threat while the DPS get into position. I don't think DPS changing targets is feasible. The reason the melee stay on Toth is to avoid Zorn's constant AOE's. I was also thinking that since Toth's frenzy is every two minutes, the melee DPS (especially if they're sentinels) should just cooldown through it. I noticed that Toth was falling behind Zorn in damage taken since the melee were running away during the frenzy.

Firebrand and Stormcaller:
Yes a tank swap is necessary. Because of that, the tanks should probably both point the bosses forward.

Colonel Vorgath:
Aren't the assassin droids present in story as well? What is different about them in hard mode, are they strongs now?

There is no problem with melee staying on Toth, but if ranged get the fearful debuff they have to switch to Toth as attacking Zorn will kill them (they get 6k per tick of damage so abilities such as telekinetic wave will result in 24k damage to the DPS) In order to avoid getting the debuff they have to be more than 25m from Toth when he jumps to Zorn, which can be achieved when Zorn is the one tanked on the left when looking at the valley from the entry point (right in the video) The DPS and healers must stand a bit to the side. I dunno why they are using melee/range on each of the bosses though, I believe this is in order to only keep the Toth's AOE from affecting 1 tank and 1 dps (the ranged is standing near the cave entrance and out of harms way, it helps he has 35m range, we might not be as lucky). Toth's normal AOE can be healed through but that extra damage was what kept killing Caravel.

On Vorgath all the adds are strongs. The droids are probably there on Story as well but they move very slow and so are easily disposed of. See this video for mixture of the 'popping' and cc'ing strategies. In here they are using a shielded Sorc, and it is similar to SOA's lighting balls (only better because of the CC)

UPDATE: from today's patch notes

BW wrote:

Explosive Conflict
Zorn's "Fearful" debuff is now correctly restricted to 30 meters.
The Demolition Probe Droid no longer attempts to move to the player in the scout tower, which could result in the Droid evading.
Minefield turrets no longer occasionally reactivate after the group has engaged Vorgath.
Kephess's Gift of the Masters ability now uses the correct (smaller) radius.

So hopefully we can finish it now. Also it looks like the fearful debuff is 30m not 25m meaning we need the tanks, or someone callign out 85, 65, 45, 25 and 5 percent HP so the ranged can move out range. Hugging the left wall (from the DPS point of view) at maximum range should help as well but by temporarily moving out of range can be the better option as it allows the DPS to go quickly go back to DPSing Zorn without worrying about waiting for fearful to wear off.

Also out of curiosity, how much damage does Zorn's AOE do and how often does he use it? Toth is about 5k every 15-20s. (don't know exactly but it's about once per my healing rotation.)

BW wrote:

Players now receive a "Timed Run" buff when attempting Eternity Vault and Karagga's Palace in Nightmare Mode. Killing Soa or Karagga before this buff expires grants the Infernal or Unyielding title, respectively.

Awesome!

Wait, so the range of fearful has been reduced, and yet we need to move farther away? I'm confused.

Pinkie Pie wrote:

Wait, so the range of fearful has been reduced, and yet we need to move farther away? I'm confused.

I don't think it was reduced, It sounds that it was fixed (i.e. it would erroneously go beyond 30m). I thought it was only 25m though.