Hearthstone goes not off of what's currently in your account, but what you've ever collected. Once you have, at least once, collected all the cards in a rarity (legendary or otherwise), duplicate (or triplicate for nonlegendary) protection wears off. This is to prevent people doing exactly what you indirectly tried to do, of disenchanting a card post nerf and then farming it.
So,my only missing legendary from the basic set was edwin van cleef wich i disenchanted post nerf but i just found a xavius wich i already had golden.
I mean,can you still find a duplicate if you have one golden?strange
Hearthstone goes not off of what's currently in your account, but what you've ever collected. Once you have, at least once, collected all the cards in a rarity (legendary or otherwise), duplicate (or triplicate for nonlegendary) protection wears off. This is to prevent people doing exactly what you indirectly tried to do, of disenchanting a card post nerf and then farming it.
simple as that,ty!