having 2 BLMs might also be an issue. I've cleared it as both BRD and BLM, but I did notice that a BLM's DPS will dip when they're forced to stack for charge, get hit with the stun, or otherwise just have to run around.
Consider having someone run something other than BLM, but there are ways to compensate. Make sure you BLMs are emphasizing crit so they get thundercloud procs and are thus more able to hit while moving.