Actually, I think that it might be that on Nutaku there's like a hidden magnet that makes it easier to re-draw defender only ssr weapons which you've already owned. I did a few 10chain pulls on the new gacha since I had 0 dark SSRs and thought why not. 2 off-element Defender weapons(got draconic eyes cuz I already had the himes), Pluto and Anubus. Like c'mon I don't even have 1/10th of the SSRs available in game, and I get 2 "repeats". This is by the way, the 4th repeat within the 3 weeks I just got back into game.