Yeah. I'm starting to think it doesn't drop unless mystery boxes is up. I've been here 4 days, opened a 1000 boxes before I stopped adding them up, and nothing.
Unfortunately I have two mules and one main character all with fishing and I needed this torque. Last two days I was in the horotto ruins and I got four "Fisher's Torques." That was without Mystery Boxes Windurst as well. After I got mine I tried to sell them for 3m but nobody responded to my shout on my mule in Jeuno.
Random is Random :/
I will say the Torque must have a higher drop rate from five guess treasure boxes then six guess treasure boxes.
I didn't have mystery boxes up when I got mine, but I also have the most ridiculous luck when it comes to torques (I've gotten several of them 1/1 or 1/2). Best of luck to you, though. Just know that you need to be in the party when the chest drops in order to actually get the item (unless they changed this at some point).
Torque doesn't help non botters much either. I wouldn't pay 10k for it. Fishing skill isn't like other crafts where you strive to get the next HQ tier. Unless it's for completionists who has to have everything, this is usually how you tell someone who didn't skill fishing on their own apart from those who did.