Toth and Zorn need to be tanked apart from each other, otherwise they get a buff to damage.
To avoid mass group confusion, we split into two teams. All ranged are on Zorn and melee are on Toth. This avoids the Fearful debuff Toth puts on during the jump phase. Team Zorn sits on the extreme left where team Toth is on the extreme right.
When Toth jumps to Zorn, anyone caught in a 25 meter radius of Toth's landing gets a fearful debuff. Basically this causes any damage done to Zorn to be reflected back to the player.
Since the fearful debuff will always hit the Zorn tank, you have to swap tanks in hard mode. The tank that was on Toth goes to Zorn, and vice versa. Toth is tanked in the same place (just different tank). Likewise Zorn is always in the same place as well. This avoids having to move the dps around.
Zorn will peridoically jump/yell. When this happens, a mental anquish damage over time occurs to anyone caught in 25 meter radius. It's a stacking debuff, cleanse immediately. Shadow tanks should be able to cleanse themselves.
During Zorn's rock throwing phase, in hard mode, a yellow ground effect will appear under one of the ops members. The player with this yellow circle must run quickly to Toth. Stand behind him and wait until it turns purple. Once it is purple RUN out of the area, the purple mark will remain. After a brief second or two Zorn throws a huge rock at Toth, where the purple mark is. If you place it too close to the other ops members, it will damage them as well.
There is a spike phase which is very similar to normal mode. Red circles on the ground will show where they will appear. Simply walk about 5 meters away from them to avoid damage. During this phase all members will have periodic damage. Make sure you keep outside the 25 meter mark as Toth usually jumps at the end of the phase to Zorn.
Avoid fearful debuff if possible. Note what the icon looks like. If you have it, announce it so you can swap dps with a member who is on Toth. Any damage (regardless of amount) on Zorn with this debuff causes you to take about 6k of damage. Any DoTs applied while fearful and you are dead.
Make sure you get both Toth and Zorn to about 10% before trying to take one down over the other. Always make sure Toth dies first, then transition to Zorn.
We generally have a melee dps come over to even out Zorn's percentage towards the end of the fight. If you pay attention to the video, you'll hear Altas call out Raithen to dps a bit. This is to make sure both Toth and Zorn are at around 10% before the final transition.
IMPORTANT: Any tanks that have a potential to inflict a DoT on Zorn when tanking MUST MUST MUST stop dps about 2 - 3% before the transition. Otherwise, the DoT will remain in affect when they get fearful, and it will kill the tank (or will get tons of spike damage).
