I bolded that part for you. You must have forgotten you said that, but to make the statement " I should also mention that to this day it is still possible to get" after bringing in relevance is moot. None of the legendary weapons are relevant anymore, by a long shot.
Testing is still being done on Thunderfury, Blessed Blade of the Windseeker as an offhand for Brewmaster Monks on high-physical damage bosses. It was pointless last expansion, when all tanks applied the Attack Speed reduction debuff that Thunderfury applies (Which was a direct stacking change put in place to get people to stop using Thunderfury, because with the introduction of Vengeance making ERMAHGERDPERFECTHREATFOREVER in Cata, there was scuttlebutt about using Thunderfury again), but that debuff was removed from the tank player abilities in MoP, so Thunderfury is back to being the unique source of high-uptime 20% boss attack-speed reduction. The only reason it's something "on the table" though, is because all of Monk's attacks scale off of your *mainhand* weapon, so sticking this rinky-dink outdated weapon in your offhand essentially means a small sacrifice in White DPS, and some stats, for a currently un-matched reduction in boss DPS. Monk bypasses the massive threat-loss a normal tank would take from equipping the weapon, becuase Monk sticks it in an ancillary slot for determining damage/threat output of abilities.
The problem with testing is, of course, monk being a new class, there's a very small set of players who actually have Thunderfury (or who even thought to go farming for it), and of that set, an even smaller number that have thought of using it/checked online discussion on it. I've been making sure to hit up MC every week since MOP came out and still only have the one binding.
Dual-wield tanking itself has some issues right now, due to bugs. The Healy-Balls Proc rate on dual-wielding is half of what it should be, so that's a direct impact to survivability for dual wielding *anything*, however that should hopefully be fixed at some point.
The value of Thunderfury is notedly higher in a single-boss, tank-swap fight, since it lets you contribute to mitigation when you are not the active tank (which, along with Ox Statue Guards, tends to make for happy healers with a Monk offtank). Coincidentally, that's what most of the fights this tier are.
It's also mildly bullshit that there is one class/spec that *might* be able to wield their old sweet looking Legendary.... and it's the one class you never see their weapons.