Was having issues with this using one tank, wouldn't it be easier with two? Even though the kill speed would be slower, it would be safer to handle? I say this because we usually don't have an absolutely decked out PLD or RUN with Burtgangs/Epeos etc.
You don't need the best geared tanks this month. Only 3 targets, and they all stop auto-attacking constantly to range attack.
A single tank with average reflexes (and a bit of practice) can hold all three Lamia on D without too much difficulty, since Frigg and Skathi don't get access to their gazes until Freyja is dead. If you follow the Frigg 5% > Freyja > Frigg > Skathi order, your tank can focus on just dodging gaze from a single enemy at a time.
On VD, it's a whole other story, since they all gaze from the start. Aside from having a tank with supernatural reflexes, you really want to try to mitigate tp-feed so the gazes aren't rapid-fire.
Tell your WHM to keep the tank in cureskin 100%. Mine sources of subtle blow (Auspice, Monk's Roll, NIN subs, gear, etc). Mewing Lullaby is also an option, if people don't mind subbing SMN.
It's too bad that many people will not try this fight w/o a PUP holding Frigg on VD. Even sadder that so many people seem to be resorting to scripts.