I've noticed this too. I know rng gonna rng but I've had a really suspicious number of dupes for legendaries. I think I've actually opened more dupe legendaries than I have uniques. The teeth-grinding aspect of it is the ones I go out of my way to craft, like sylvannas, Dr. Boom, and Rag, I ended up getting a duplicate of each within a few months. It's a conspiracy. I've seen 3 tinkmaster oversparks and two nozdormus, 2 king mooklas, and a rag/syl/boom shortly after I crafted them. I think cenarius is the only legendary I opened that I use in my decks. I recently crafted harrison so just counting the days before he reveals himself.