If i have every item out of molten core minus the left or right binding (depending on what character im running) you would think… You lovely or loveless birds would have a system in place that loot tables narrow… not just some crappy 5% buff that if you have bad Rng you are already screwed.
Sincerely a guy who got excited about collector’s bounty because his RNG has always sucked.
Your RNG is not the indicator for success.
Binding’s are already a ~5% drop now they are ~10%. I’ve had 4 Thunderfury’s before this event.
RNG is RNG, if an item had a 99% drop rate there is still a chance for someone to not get it in 5+ runs.
Keep running it on all of your characters who can equip a 1-handed sword because chances are, per Murphy’s Law, a character with 0 bindings will get 2 bindings in 1 run.
Just like my buddy who had for the longest time 1 warglaive on his DK, Rogue, DH, and Warrior and during this event for laughs he ran his monk through and got both in 1 kill.
Kinda the point i’m making though…
So you expect Blizz to add something like bad luck protection for content that’s beyond outdated? They can’t even be bothered to fix bugs that pop up in old content unless it breaks the game.
I’ve been running 16. I had a random 42 paladin get right binding last week. hundreds of runs still zero characters with both.
RNG giveth RNG taketh.
Just keep trying that’s all you can do. Some people have never gotten Invincible who have been farming for 12+ years every week and sometimes a new player kills Heroic 25m Lich King for the first time and gets it.
Just this time you have a 10% chance instead of 5%. Also I’m the same for the Core Marksman Rifle recipe which never drops for this character for my collection 
those old Soulbound recipes need to be Warbound.
If blizzard valued time this would be the greatest game forevermore. 