Reading the patch notes i found this

"Entering the Labyrinth of the Ancients
The Labyrinth of the Ancients can be accessed via the Duty Finder when playing solo or in a party of eight players. However, parties that enter the Crystal Tower must fulfill the requirements of two tanks, two healers, and four DPS. Please be aware that you cannot register for this duty if your party does not match this composition.

Please note that three parties of eight cannot register for this duty together. Each party must register separately and be matched via the Duty Finder"

It is the last part that got me : "Please note that three parties of eight cannot register for this duty together. Each party must register separately and be matched via the Duty Finder"

SO even if you have 24 people in your FC / LS one you might not all be matched and two you MUST fill the roles .

Thoughts