Just a small update to let you know what is happening. We are currently focusing on learning Archimonde.
The key to this fight is staying alive. Someone dying is a lot like someone moving in Flame Wreath at Shade of Aran. It gives Archimonde a Soul Charge which he can use at the raid. Depending on what class it was that died the Soul Charge has different effects.
Priest, Paladin, Warlock
4500 fire damage within 200 yards and a 4 second silence.
Warrior, Rogue, Mage
4500 physical damage within 200 yards and all damage taken is increased by 50%. Not sure for how long this effect lasts. Armor mitigates the physical attack.
Druid, Shaman, Hunter
A 4500 nature DoT (1125 every 2 seconds) and 2250 mana drain within 200 yards
If someone dies it's very easy for more to follow with these effects taking place so it's really important for everyone to stay alive. There are Doomfires crawling around on the ground like snakes which has to be avoided or they do a lot of damage and leave a nasty DoT, there are Airbursts going on with 100% fall damage which you have to use an item you get from Tyrande to survive and of course he also regularly fears you right into those Doomfires so PvP trinket and staying far away from Doomfires when Fear is approaching is vital. There is also Grip of the Legion, a curse used very often which does 2500 shadow damage every 3 seconds for 5 minutes. It should be decursed immediately.
We haven't had any proper DPS attempts yet as we are just focusing on staying alive to learn the fight. Most attempts we live for 3-4 minutes, we have survived for 9 minutes once and at best we've gotten him down to 48% health.
The guides I've seen recommends not using Tree of Life form as there is a lot of movement to avoid things. I started without it but now I'm fairly comfortable around Doomfires and I shift a lot between tree, travel form and caster. I stay in healing range of the MT as much as possible and use all 360 degrees to do so. We have 2 separate melee groups and 3 ranged groups. If you position correctly then 20% movement reduction helps you to not run into any Doomfires. There is also cheaper spells and healing aura to consider. If you can handle Doomfires and still go tree I recommend it, it's important that there are others to decurse of course. If there isn't then you should probably skip tree.