yea i dont know how they did this, from watching the video the person recording doesnt ever take any damage besides from momento and it looks like the king and mrd are on the gla the entire time, i dont know if they got really lucky and the moogles never called for help or if their tank is just that good, or if the person recording just is on the low end of the damage output but they make it look really easy.

Their kill order by the way was BRD BLM WHM THF ARC MRD KING GLA