I got 10 bunny slippers in a silver chest yesterday. They don't happen often, but they do happen in the boxes once in a while. I loathe farming them. They only drop in one level, and the drop rate is terrible. This is something that I recently brought up. I hope that it will be addressed soon.
I too am in that Snap Dragon has to wait boat. 3 slippers for 120 stamina is asinine when you consider how many of them are needed across the board for several rarities, and quests. It takes something like 840 stamina to farm a bunny slipper. If not a higher drop rate, they need to be introduced into some of the newer levels as a secondary drop for orange item levels. Grinding that one level we have on server seven yields hundreds of blue scraps that are no longer needed for anything except enchanting. Basically, we have to keep swimming in the kiddie pool to work heroes that are ready for the Olympic pool.