After some digging, I found in another post on the forum that the drop rate bonus only applies to groups. I was grouped when I was getting the increased drop rate and solo when I wasn't. I was in Chaz farming tier gear using housekeeper luck potion both times. In previous drop rate bonus events it applied to solo players. It's a shame that RoM did not make that information known in the event announcement. It's going to upset a lot of players.