I'm writing this for my benefit as much as you guys
After spending many hours in this dungeon with a PuG I have found a few things out that really can't be found anywhere else.
I mean alcast gives a good over view but (probably because he had a good group) missed a few details.
A tank is absolutely necessary, same for a healer. Seems to me dps is the very least Important thing, mechanics and movement is very important
The first boss, Ogre twins.
Keep them away from each other. One is immobile in the middle, one runs around.
The running around one has a charge up punch that one shots non-tanks
Boss pattern: you will get a message about being targeted by an ice tremor, jump into one of the yellow ice AoEs. It will freeze you, you can break free - do not break free. Allow the tremor to hit you, it will break you free and prevent damage. 1 AoE per character. 1 shot mechanic
Then Ice pillars will form (2?) Hide behind them until Ice Ball pops shattering pillars
Middle ogre slaps ground summoning skeevers, interrupt this.
Pattern repeats - kill both as close to each other as possible - once one dies impossible to prevent the next 1 shot mechanic
Boss 2 - gargoyle and floating balls
Gargoyle - boss bleeds tank (gotta have a tank) healer should focus on tank.
I actually found that after a player becomes encased in stone the gargoyle does the Lazer beam channel which is interruptible (you may already know this) but what you may not know is that after you interrupt the channel the gargoyle becomes enraged and does a small AoE attack. During this attack all lazers stop and it becomes a very good opportunity to free allies.
Every 10% floating ball that shoots lazers appear. If too close for too long will make you a statue, if happens ally must free you quickly (or interrupt boss) to prevent 1 shot. Dps should focus ball once it appears. Really rinse and repeat, saving allies asap
The wind up hit does very high damage, many builds will not survive this, use caution as a tank. A source of major Expedition or a teleport move can be quite convenient.
Boss 3 - Giant Lady Matriarch
Really 2 important mechanics, focus adds when appear, tank plugs hole in the ground when appears. Healer focus tank in hole. Adds must be killed to prevent high damage attack. Also standing in water hurts you.
The holes will appear in front of the Ads.
Boss 4 - Poison Archer Guy
tank should just tank boss, again there's a plug hole mechanic involved, healer focus tank during plug.
Important : everyone will be poisoned. The NPC will yell out something like, "I need Imp entrails" or "I need sapling root" etc. Adds will appear, kill two of the mentioned adds and the NPC throws out a potion to heal the poisons and provides buff. A small green AoE appears in the middle of the room.
Note- after each potion is thrown the boss will fall to his knees and then yell out "what are you gonna just sit there and watch?" Or something like that. A strong guard capable of 1 shotting does will spawn. It's highly advised to kill them asap or have tank taunt them.
Zaan:
I've done this boss now to know her inside and out.
Her normal attacks are small AoEs and if blocked don't pose much threat at all. Even unblocked most tanks will survive, they however will knock you down for a moment which can spell death once the AoE 1 shot mechanic starts (more in a moment)
She will occasionally target one player with fireballs, these can be easily side stepped, if you are squishy or worried about them there is a pillar on the "left" (facing the dragon statues) you can stand behind and it will block the blasts.
Her "chain" ability will occur after a semi large AoE that (kills non tanks, but tank can survive) but will knock player down. She then pics a player up into air and a beam appears dealing massive damage. It's advised non tanks stack behind tank for this part, but you don't have much time nor coordination with PuGs. If non tank is picked, the tank can just stand in beam blocking, if tank is picked it seems best the whole group just mob it and get out if too much damage is taken.
She Summons Ice Giants with approximately 50k health, you have 10 seconds to kill them both or you all wipe.
Then comes the fun part.
Watch the dragon statues, one will light up indicating the area in front will turn into a giant AoE. Get out ASAP, if you're even close enough to think you're touching the AoE you die.
The AoE is random, and seriously get out, don't finish the rez (the only real reason people get caught in one after a while) just get out.
She then throws her shield and a green AoE appears in the area, get in there asap, it's advised to heavy attack for resource Regen now)
Once full area AoE is gone get out of shield AoE.
Rinse and repeat without making a mistake!
BTW range taunt highly recommended!