The Assault has 1 Lamia Boss. She is pretty weak but has a Charmaga AOE. There are also 3 NPCs - Fallen Mage, Volunteer and Soldier she has initially charmed and help her fight.
Now the trick has been uncovered that you can dipel the charm that is upon the NPCs. Here is where you need 2 mage friends - BRD RDM or sub RDM. You will go in with just 3 people to max out the reward you get. If you are lucky like me you have a mage job up ,too. But going in NIN/WAR as "leech" works, too.
Approach the Lamia and asign targets. One of you takes the Mage for dispel target, one the Soldier and one the Volunteer. If you are NIN/WAR you voke your target so it doesnt harm the mages and let it be dispel after by them.
After beeing dispel the NPC will start whacking onto the Lamia. The mean thing now is she can recharm them with their AOE so stand back and repeat your inital maneuver. You can even cure the NPCs without getting hate linked onto you. You can even Haste and Protect them but.. whops... when they get recharmed you might hit their Haste with dispel but not the Charm - so dont buff them.
WHATEVER YOU DO - do NOT touch the Lamia 13 itself. Even if she sees and aggroes you she wont have any active hate towards you. When she charms the NPCs she will just unaggro and not go after you unless you are too close.