If you really wanted the weapon you could just play as GNB. You have it leveled. It would make your chances much much higher. At most the weapon would be free or you only compete with the other Tank.

Alternatively you could have asked prepull if the GNB weapon drops could you have it as you have a lvl90 GNB that could use it as an upgrade OR offer them Gil to guarantee the drop?

While I find it was rude and unfair to others I have to applaud the player's cleverness. And that as they are seemingly a master ninja looter they deserve all the respect a Lominsan Rogue deserves.

Although if you are doing Savage content on a different class one might argue why roll for the weapon if you realistically can't gear up multiple jobs and should focus on your main instead?

They really need to change up gearing with the whole "you can level every job" but you can "only gear up one".