Drops work in the following way:
1. Kill a monster
2. Roll for a single item from each chance table (common, uncommon, rare... etc)
3. Roll for each of those items
4. Pray to Pickles
5. Win a roll, get the item being rolled for
Previously there was a bug where it was rolling in the wrong order: from most common to most rare. This bug has been fixed so rare items are now rolled for first, thus balancing the drop rate on many items (Whips and such).