Barspells, Misery Esuna, Silence Housemaker (can still call over his friend even if silence is applied, but silence greatly lowers thsi chance), sleep adds. Pretty standard, with double the HP I'm sure. it was a fun fight before, I'm actually looking forward to tanking this one. RUN should be participating in the DPS, if you go that route. Looks like multi-step was the better way to go for huge spike damage.
last time this fight came around, there was an unusual mechanic where I died without taking any damage in the log. Just completely dropped mid-fight. Nobody in the party knew what was happening, but it only happened once. Perhaps battlemod just didn't record it, but it seemed odd.
One thing that was rather funny, watching the one meeble chase the poor whm or geo all over the battlefield, just to use earthshaker. iirc, it will always be the person using barspells, or someone low on the hate list. Someone will usually die, every fight. The range is not very large, but you can manage to avoid this move hitting the party if you see him charging over and you get out of range quickly. Will help save a few bodies.
One of the dangers I recall is the virus move, which can lower you to somewhere around 500~ HP. This is particularly dangerous if not removed quickly as it will drop the tank almost immediately afterwards. Good to have Panaceas on hand.