Since I went from combat lvl 91 to 119 while mostly 99% from dust devils with RoW, that is about 60k kills if i calculated right and no d chain -.- , i only got like 3 shield left halfs and 3 d spears from them, my theory is because i always teleport to restock and bank the items, and that getting a rare drop is based on how long you actually stay in the dungeon, people use bones to peaches to do that and they usually get a d chain within 5k or 10k kills, i even got 2 left halfs from only ranging about 500 dusties but that was very slow. But yea, all the total drops value probably averaged at way higher than a d chain, and the exp from them was worth it (since dusties have high hp, low defence, and low att + str, and theres a lot of them together, plus it's fast to get there if you home tele) it still would be nice to get that d chain bonus lol.