Quick Summary of First Boss (Long but worth the read)
The bosses have energy bars, if there is another guard within 12 yards of a boss he will gain energy. The opposite of this is if no boss is within 12 yards the boss will not only not gain energy but will also take 90% less damage.
Jade/Jasper/Amethyst/Cobalt Petrification: The boss which is empowered provides 90% damage reduction to a corresponding element (Nature/Fire/Shadow/Arcane), allowing you to counter the their abilities, both the explosion (see below) and the secondary ability they are putting out (Nature AoE/Fire Chain/Shadow Pool/not actually sure what cobalt does but I believe it is a arcane land mine debuff). There is a stacking component to this which reduces move speed, and if the stack reaches 100 you are permanently out of the fight (just like the 2 trash mobs)
Jade/Jasper/Amethyst/Cobalt Overload is a raid wide AOE that happens when a boss reaches 100 energy and does massive elemental damage depending on which boss is doing it. Eventually something will explode or you either perma-petrified, not to mention you will be doing 90% less damage. The goal is to make the empowered add explode because that explosion will be reduced by 90%.
Boss Damage Type (vs raid):
Jade Shards: A nature AoE that happens throughout the entire fight, damage reduced by 90% while Jade is empowered
Fire Chain: Connects 2 people with a fire chain that will deal massive damage when to far apart (but no damage at all when they are near each other), but being apart is the only way to remove it. During Jasper empower is the time to run away as the breaking damage will be reduced by 90%
Shadow Pool: Amethyst will place shadow pools under people the entire fight, but because all the empowers cause a slow you really need to be on you toes to move out of it in time. During Amethyst empower it is safe to stand in them at their damage is reduced by 90%
Rend Flesh: Massive bleed damage on the tanks, all the bosses can apply this but it does not stack and cannot have 2 stacks on a single tank
Tank A will always grab 2 of them and Tank B will pick up the third while you wait for the first empower. For purposes of simplicity the tank with 2 bosses with be Tank A and the tank with 1 boss will be Tank B (note: this designation is constantly changing during the fight). At this point one of 2 things can happen.
If either of the bosses in the 2 stack empowers:
Tank B will taunt the empowered mob at 50 energy and become Tank A
If the add being solo tanked empowers it gets a bit more complicated:
Tank B needs to instantly taunt either of the other 2 bosses, which one does not matter just do it quickly.
Wait a bit until the non-empowered boss in the 2 stack hits 50 energy the first tank taunts the empowered boss back
In both cases, Tank B will have a single boss with 50 energy and Tank A will have one boss with 50 energy and another boss with 0 energy (the one that just exploded).
The Rest of the Encounter:
After that the fight will continue as normal in a "set" pattern, and that pattern is that an add cannot empower twice in a row. This limits the the possibilities to 2.
The single boss gets empowered:
Tank B taunts the boss that just exploded (will always be the one with 0-10 energy depending on the delay between explosion and the next empower)
A boss already in the 2 stack gets empowered:
Nothing changes, tanks keep what they have
If this happens 2-3 or more times in a row and you are Tank B, this is where the fight gets very tedious. You are basically doing nothing for minutes of the fight at a time but keeping up your defenses. Right now that is your only job other than keeping track of what to taunt when your boss finally does get empowered.
In rare cases, it may line up in a way that the second (non-empowered) boss in the 2 stack will explode shortly before or shortly after the empowered one.
Simultaneous taunt across the room and swap non-empowered bosses. Tank A stays Tank A and Tank B stays Tank B but what you are tanking has changed.
That is literally the entire fight for tanks: making sure you taunt the right thing and move out of pools if one should spawn under you.
The main source of damage on the tanks is the Rend Flesh so you are basically a giant damage sponge trying not to die.
The most effective time to use your cooldowns is while Jasper is empowered.
While Jade is empowered the AOE damage is reduced by 90% so healers are already focusing on the tanks more.
While Amethyst is empowered the damage from the pools is reduced by 90% meaning there is more leeway with moving out of them, allowing healers to finish that big cast on you.
Since they share HP and when you are only tanking 1 thing that particular one tanks 90% less damage always use berserk or when you are tanking 2 things, preferably 2 things during jasper (caveat: late in the fight you are tanking one thing and healers are oom and you need lots of rage income then anything goes).
The guide linked by Kappak goes into far more gritty detail but I find it does not do a very good job of focusing on a "how to tank" summary, making it a bit confusing. Since this fight is simply about 2 tanks working a mechanic perfectly for 5 to 10 minutes and the rest of the raid DPSing and healing and not standing in bad stuff etc...wanted to post this Tank summary here.
See you all tomorrow,