From Rast on PTS forums:
My guild and I just defeated the first boss in the new operation on story mode, and I wanted to post an overview and some thoughts.
You Tube Kill Video
(A healing perspective. I was tanking. Hopefully this gives you an idea of the fight itself however.)
We usually run 16-man operation content. Tonight on the PTS we just did an 8-man clear. We have cleared all live content on nightmare difficulty, and we have obtained the titles from timed nightmare runs in both the Eternity Vault and Karagga's Palace, multiple times. Tonight, prior to trying the PTS, we cleared nightmare EV in roughly 60 minutes. We are nearly all in full Rakata gear.
We ran with two vanguard tanks. We had one sage healer and one scoundrel healer. Our dps consisted of a sentinel, a commando, a sage, and a gunslinger.
The fight consists of two boss mobs that must be tanked apart from each other. The mob on the right as you face them is Toth and the mob on the left as you face them is Zorn.
If the two boss mobs get too close, they gain a stacking increase to the damage they do and will quickly destroy the tanks and subsequently the raid. There is a beam of lightning that connects the two boss mobs if they are too close. Both mobs were dps'd simultaneously. At roughly 90%, Toth will leap to Zorn; any player (from what we could tell) that is within 30 meters of Zorn is given a fearful debuff; this will dramatically increase the damage they receive later in the fight. This mechanic is avoidable by all members of the raid except for the tank of that mob and potentially the healer on that tank, although this requires some careful play.
When Toth leaps to Zorn, the tanks need to swap the mobs they are tanking due to the fearful debuff. Zorn is still tanked on the left and Toth is still tanked on the right. However, the tank that was initially on Toth will now be tanking Zorn and vice versa. Neither the dps nor healers need to swap unless they get the fearful debuff. Our healers occasionally had to swap sides; no dps needed to swap on our kill attempt.
Shortly after this tank and position swap, a system warning will be sent stating that Toth is enraged. When this happens, Zorn will start to throw rocks. Anyone with the fearful debuff will take massive damage from these rocks. However, if you are at 30 meters or greater from Zorn, you will not be hit, at all, by any rock damage. We found that even the tank needs to run out or else the damage he or she takes is just too much to heal through.
Shortly after the rock/enrage phase ends, the Toth will again jump to Zorn. The tanks again swap what mobs they are tanking, return the mobs to their original spot, and the raid resumes dps'ing and playing. Soon after that tank swap, the Zorn does a sonic yell cast--I don't remember the exact name--and while this is happening Toth pounds the ground consistently. Red targets appear on the ground, and, not surprisingly, you need to run out of the targets quickly or you take damage. The damage wasn't massive and mistakes were easy to heal through here.
Additionally, the Toth will occasionally do a massive, huge aoe knockback. This knockback is proximity based, but due to the large aoe, it seems tol invariably hit multiple members of the raid.
After both Toth and Zorn are defeated, a champion mob that starts the fight standing on the ledge jumps down into the pit you're fighting Toth and Zorn in and must be defeated. He is a very quick, simple kill. He had roughly 150k HP.
That's the fight. Tanks swaps with the associated rock phases and target phases will occur at least twice. Just stick to the above strat and the bosses will die. We noted that, during the last 5 to 10% of the fight on a few near kills and then on the actual kill, the two boss mobs may start to simultaneously do both their rock/target abilities. This may have been a hard enrage or may have been a bug. We had this on our kill attempt, but we survived it too. This seems to be a normal mechanic of the fight, but with only a few limited attemtps, I may be wrong here.
The fight was a lot of fun in part because we were figuring out new mechanics and new strats. Having the Zorn tank run out of the rock phase made the fight much easier. The damage--even without fearful--the tank received from Zorn's rock phase was crazy.
The fight was fun; however, it is currently tightly tuned. As we were learning the fight, we hit the enrage timer several times. This was much harder than any normal mode EV or KP fight--even assuming fresh 50 blues and oranges from questing. The healing required was a step up, the damage done was a step up, and the margin for error was a bit less than EV/KP fights. This fight will obviously get easier as strats are refined. It was not an unfair fight; it was fun to have a challenge. I'm worried, though, about expectations. If people expect to walk into this new operation in 50 questing gear, this is a rough, rough fight to experience. I can't imagine an operation of new 50s downing this fight without intense experience. It felt more like a current nightmare mode boss in EV or KP than a normal (story) mode boss.
We noted at least two bugs. First, at least once the mob jump didn't happen and as such the tank swap didn't happen; this quickly lead to a raid wipe. Second, the rock warning red text did not appear once only to appear later in the fight at the wrong time. Our sage dps and healer, as well, had a hard time casting their ground target aoes. It appeared to be related to the ground the mobs were stood on.
I'm a tank. As a tank, the only HUGE frustration I had with this fight was the massive number of threat drops. Every boss jump was a threat drop and each rock or target phase seemed to end with a threat drop on one mob as well. Seeing these frequent threat drops even after Georg Zoeller acknowledged how unpopular (lame?) this mechanic is was disappointing. Our dps and healers definitely noticed this. As a frequent, regular taunt is a key part of this fight, if threat drops a tank may or may not be able to immediately taunt; his or her taunt may need to be saved for the boss jump transition.
Overall this was a fun fight; a few other members of the raid will hopefully comment on their perspective.