I remember the time NegurA killed Fafnir with 6.
...With a RDM tank.
About NegurAs strategies. They have gotten Fafnir down to 20% in about 5 minutes numerous times and then just let it sit there. It's their claim, their hour, and they can do what they want with it. Don't like it? Petition for a shorter rage timer.
I was killing Fafnir/Nidhogg with KI and NegurA while the entirety of Sylph's current end-game was levelling their subjobs in Valkurm.
(And this is purely from a neutral perspective, I don't play FFXI anymore, and don't really care about drama between guilds on my old server.)