New Living Story Boss - The Marionette

Some of the information I've found that you might find helpful.

Scarlet Marionette

Standard Dulfy guides!
http://dulfy.net/2014/01/21/gw2-scarlets-secret-lair-guide/

http://www.reddit.com/r/Guildwars2/comments/1vt6ol/marionette_lane_order/
This is a discussion about the Laning situation and how the portals into the Marionette work.
https://i.imgur.com/zASH0eD.jpg
An overview they made which shows rotation of the portals opening.

Great explanation of the encounter.
Source:http://www.reddit.com/r/Guildwars2/comments/1vu05c/lane_jumping_for_the_win_in_the_marionette_fight/
The fight consists of two phases:
All 5 lanes leading to the main arena come under a constant assault by champions and veterans, and players have to keep the mobs from reaching the end of the lane. Many players consider this the easiest part of the fight, and that it may only take 10-15 players to handle this phase in each lane, as a good team can wipe out the mobs right at their spawn.
Starting from the southernmost lane and moving clockwise, the assault recedes from one lane and that lane's players have the opportunity to teleport up to the main arena. They're randomly divided between five champion arenas, face off against a champion. Once the champion is killed, they can destroy a power relay on their arena. If all five relays are destroyed, a marionette string is cut. This is the hardest part of the fight, and many estimate they need 20-25 players to complete it.
Players from the arenas are teleported back to their lane and given a Sickness debuff to prevent them from using one of the other lane entrances. This debuff lasts ~5 minutes, which is about two rounds of fighting.

Part Two: Champ fight- So what I've seen, every group needs to defeat the champ in their respective circle. There are different types of champs that have different mechanics, so read the champ description.
These champs are based off of chain order. So the second champ comes after the first champ is cleared, etc.
First Champ Must shoot from behind. Cannot damage from front
Second Champ Must drag through own bombs dropped. Cannot be damaged unless stunned by own bombs
Third Champ Dodge the bombs and the KDs. Other than that, fairly simple
Fourth Champ Confusion scream, and shoots missiles. Confusion stacks, so be careful and time your rolls.
Fifth Champ Splits when defeated, similar to Subject 7. I believe it once defeated, it splits a total of 4x. This one is a DPS fast.
Source:http://www.reddit.com/r/Guildwars2/comments/1vsiyi/marionette_fight_tips/

If your struggling to get in with friends :>
https://i.imgur.com/8TayNfd.gif
http://www.reddit.com/r/Guildwars2/comments/1vtopj/how_to_participate_in_the_marionette_encounter/

Killed it last night on an overflow.

It's not really hard as long as people know what to do.

We just killed it on GH this afternoon as well

I think its a fun event, but its a bit of a farm again getting 25 of all those pieces and 50 of the other, ah well it keeps us busy and gives all of us some achievements

Did it yesterday as well , though we failed at cutting the chains , other then that epic boss and fun to do