I had the same frustration. Ironically, for me it was getting a drop of a mark on my Titan. Eventually I got all three characters to 1060/1080, but the dups did lend themselves to a lot of annoyance. Statistically, if you are seeking a gear piece, try to find a way to do Prophecy and The Pit every week, since they only drop gear. It’s sort of a slog, but you will get that missing piece. Based on my own drops, my sense was that RNG is weighted so that the Gambit, Crucible and Strike pinnacles are more likely to produce weapons (which may be to compensate for the exclusive gear drops from the dungeons), with what seemed to be a strong numerical advantage to kinetic and energy weapons. The Interference, clan, 100k NF, and Master Nightmare Hunt pinnacles all seemed more balanced in their drops, though I got a ton of duplicates from all of them too. Same with the pinnacles from Iron Banner, where you make a lot of progress but need to wait four to five weeks. The Garden RAID obviously also helps, but seeing as I have yet to complete it, I can’t speak to its drops.