Someone pooled a bunch of people on Reddit for the Vex drop rate awhile back and they found that the actual drop rate (unless Bungie flat out tells us) is around a 2% drop rate and you get +1% or so every clear that you don't get it. So if you have 36 unique (3 per week) clears, you have roughly a 38% chance to get it as of now. But you also have to compete with the other weapons and armor which have their own, way higher drop rate. My drops for raid exotics we're - 50 runs to get Eyes of Tomorrow - 83 Runs to get Vex Mythoclast - 9 to get Anarchy - 11 for Tarrabah - 7 for Collective Obligation. Then we go to my friend Cake, who has gotten every raid exotic within 5 runs. He hasn't gotten the new pulse yet, but he also doesn't raid that much anymore and only runs 1 character. 🤷 Needess to say Bungie's RNG is a real B**ch.