My guild uses a loottracker created by Procat from Lazy Monkeys and also used by THU on Newfoundland. It involves players inputting their adv loot manually into the site to keep track of their personal loot, and provides a good global overview of all loot drops on all adv. Whirlwind was added to this site on 7th June and in the 64 loot entries for whirlwind since that date, 3 have had bone churches drop.