Another officer created this guide, so I will be posting it here and adjusting it so this is a very much WIP. Screenshots to be expected.

See guide for Moon Hunter Keep

Boss locations:
The Wyrd Sisters: There are three bosses here, each with their own aura surrounding them. Keep the sister's out of each other's AOE buffs.
Ursus (Sword and Board Boss): Green aura, unknown affect (thought to be resistances buffs for nearby allies). Heavy attacks must be blocked by the tank, and this will one shot any other player through blocks. Will occasionally Charge a player, knocking them back and doing moderate damage to them. Block if seen coming.
Rangifer (Healer): Yellow aura, unknown affect (thought to be healing received buffs to nearby allies). This boss has strong healing effects for her allies, including the common tether healing beam other healing NPC's have, and a ground AOE healing effect.
Strigidae (Nightblade Archer): Blue aura, debuffs players with Silence. The archer has a snipe that needs to be interrupted otherwise it will one shot a player, including tanks if not blocking. The archer will occasionally teleport strike a random player, making her aura go in undesirable areas. Stay out of her silence as it blocks all magicka based abilities, ultimates and synergies.
When one is killed, an animal aspect of them will spawn with the aura still in effect. The aspects will go to their closest living sister to give that sister the buffs from that.
Tank: Taunt the Ursus, the sword and board boss and keep her away from her sisters.
Healer: Stay near center, healing all the players.
DD: Ideally you want all three to die around the same time so the animal aspects are not causing issues. The best strategy my teams have found was to focus the Healer, and once its dead then DPS split between Ursus and Strigidae.

Aghaedh of the Solstice: The boss has four mini Spriggans around it with AOE's attached to them differing in color: Green, Blue (Slow), Orange and Red (Damage). These abilities have different effects, so you do not want to stand in them until the Seasons mechanic. Four Lurchers will spawn throughout the fight each with their own color, Green, Blue, Orange and Red, same colors as the AOE's. When a lurcher dies, it'll drop a matching glowing light on the ground that needs to be picked up with the Synergy button. Each player will need to pick up their own color. The boss will start a channeling ability, and each player must stand in the circle matching the color they picked up.
Tank: Taunt boss and all Lurchers to boss so that they all can be cleaved down. Do not forget to pick up a synergy when a Lurcher dies.
Healer: Group will be close for most of the fight except for the mechanic, so be sure to get out heals when the group splits to the different AOE's.
DD: Cleave down Lurchers and focus boss. If DPS is on the lower side, then focus the Lurchers.

Dagrund the Bulky:
This is an elemental boss, and he'll do a variety of attacks taking the form of fire, ice and lightning. Periodically the boss will raise his sword up in a channeling animation to send out elemental AOE's. Fire will spread out from boss then bounce off of a wall once; ice will spawn under the players feet and lightning will be hitting everyone over time that needs to be healed through (easy to do with self heals).
Dagrund will leap into the air every once in a while (on timer of about 60 seconds) that will send out four elemental attacks that will home in on each player. This WILL one shot every player, unless it is blocked or dodge rolled through. DPS is highly recommended to dodge roll through because you'll still take a lot of damage through the block.
Adds will spawn, thought to be at health percentages, and each add will have elemental attacks as well. Fire adds will spawn fire aoes that will stay until the add is killed. Ice adds will slow the players they hit, stacking the snare.
Tank: Hold Boss still, near spawn point. Adds cannot be chained in so don't bother with them.
Healer: Stay in center to heal whole group. Send out plenty of resource gains so that group has stamina for block and dodge rolls.
DD: Focus adds whenever they come up, noticeable by dialogue. Do not ignore adds until boss is under approximately 15%, then you can focus boss. When boss jumps, try to gain distance so you can see the homing AOE and have time to counter it.

Tarcyr: Hunting Phase: When you first enter this arena, there'll be heavy fog flowing through it. If you do not enter stealth, you'll find yourself be teleported into the air and you'll take fall damage. This will occur any time that you break stealth or are detected during this phase.. Every time you're teleported into the air during a single phase, the higher you will drop from until the third time you will be killed. This phase also occurs at health percentages of 80%, 55% and 20%. Immediately enter sneak and spread out two the four cardinal directions of the room when notification of the Hunt beginning. Be mindful of your stamina, and for Magicka toons, Vampire is recommended for the stealth movement buff.
Wisp: A friendly wisp will be floating around the area. When the wisp lands on a location, it'll have a green AOE around it, and a player must go to that Wisp and Synergize it. This must be done three times for each phase. It will then find the boss and you can exit stealth until the next Hunting Phase.
With each progressing Hunting Phase, there are additional attacks to watch out for so that they don't pull you out of stealth. Stampeding Indriks, Ice AOE's spawn under your feet, Fire bouncing off walls and an Ice AOE that spawns on two random players and sticks on them. The AOE on players is why players need to stay spread out, so another player won't go near the AOE'd player and be revealed. When the Wisp is no longer moving and with all these AOEs, it is best to call out who is going for the Wisp.
Hint: If you are teleported into the air, you have a few seconds to re-enter stealth. So cast a self heal as soon as you touch the ground then go in stealth.
Hint: Do not attempt to resurrect a player during Hunting Phase as you will be instantly revealed.

Tacyr Abilities:
Light Attack: Tacyr has a frontal cone cleave attack so do not stand in front of the boss.
Stampede: Tacyr will rear up and send out ethereal Indriks at each player. Block or sidestep them, otherwise you'll be knocked back and dealt a moderate amount of damage.
Fire Rampage: Tacyr will gain a shield and start rampaging leaving a firewall in her wake. Very simple to stay out of those.
Lightning Prance: Tacyr's most dangerous ability is when she starts prancing in place and casting lightning to all players. This lightning ability will wipe the group within about two or three stampedes, which is within about two seconds. It MUST be bashed or interrupted immediately.
Hint: Often right out of a Hunting Phase, Tacyr will start her lightning Stampede so be ready for it. Do not get resurrections until she has been interrupted of that phase.

Tacyr Adds: Every now and then adds will spawn in, and they are a huge threat if they get off their channeling ability. This will Bolt Trap a player, which stun locks them in place and can be very deadly if at the wrong time. To get a bolted player up, another player must go over to them and use a Synergy.
Hint: If Tacyr is pushed to her next Hunting Phase, the adds will be killed by the mechanic and are no longer a concern.

Tank: Turn boss whenever possible, and be mindful of bashing the lightning prance. Adds are not a priority, but they can be taunted in.
Healer: Lots of resource abilities need to go out so that all players have resources to interrupt the lightning prance. Do not attempt to heal while in a Hunting Phase as this will reveal you. If you have long lasting HoT's, refresh them right before the Hunting Phase beings.
DD: Focus adds when they spawn.

Balorgh:
There are three islands in this last area, and you must pay attention to those islands. Commonly referred to as Left Island, Right Island and Exit Island (facing into the arena). The boss will do a ground slam that will make poisonous spores spawn on the three islands so you must be off of them at this point. After that, the boss will do a lightning attack that will electrify the water and you must fight the boss on the islands.
Hint: After each phase, move to the one that just ended so you're ready for the next phase. I.E. After island poison AOE's are over, move boss onto an island so that when his lightning attack comes, you're all already out of the water. When water is no longer electrified, move back into water so you're off the island for the next poison phase.
Darkness: At health percentages the arena will be covered in darkness and fog. One random player will recieve a targeted AOE under their feet, and this player will be targeted by the enraged boss. Keep your distance! A blue pillar of light will spawn a few seconds after the initial darkness spawns so keep searching. The light spawns are: Entrance, Left Island, Right Island, Middle Island Left, and Middle Island Right. The targeted player must pull the boss THROUGH that blue pillar of light. All group members should be going to that pillar of light as well so when boss is broken out of the darkness, tank can take immediate control.
Darkness Adds: During the dark phase, several wolves will spawn in. The longer the dark phase last, the more wolves that spawn. These wolves have an uncleansable snare that will stack. Beware them while trying to search for the blue pillar of light. The wolves will stay after the dark phase ends, and they are a big threat with their snare so they must be cleaved down.

Balorgh Abilities
Ground Slam: Large AOE around boss that must be avoided. Only the tank can survive it if blocking, but still highly recommended to get out of the AOE.
Breath Attack: A conal attack that will follow the target, usually the tank if taunted. This conal attack will kill anyone other than the tank instantly so tank must keep boss turned away and not turn boss while the attack is ongoing.