Just because DRK cleared ultimate first doesn't mean it doesn't need buffs

[Bourne_Endeavor]

The obvious question is, "Why would two world first groups use the 'weakest' tank in the 'hardest' content?"

Is there an obvious answer? I don't think so.

For the same reason Angered initially ran Samurai then Monk when Dragoon/Ninja is clearly more optimal. They found it fun. Yes, Monk helped with Mantra, but at the same time, unless fights have an incredibly high DPS check, comp won't have a significant impact unless you're speed killing.