I just finished making a script that takes in consideration all exotic weapons and armors that should be obtainable, and not PS4 exclusives. Check out https://verifyup.com/xur.php it's based on the 21 weeks xur has been in the tower, and it randomly selects 1 armor type of each class, and 1 weapon he could sell. I'll update the data with the actual results as well to see a comparison, does anyone have that data already available though?