http://2007.runescape.wikia.com/wiki/Rare_drop_table
"The rare drop table is a special list of items. When slain, some monsters have a chance to give loot from the rare drop table instead of loot from their own unique drop table. This chance usually ranges from 1/16 to 1/64.[1] Unlike the standard drop table, the rare drop table is shared by many monsters ranging from chaos druids, to lesser demons, through to most Slayer monsters and the Kalphite queen.
A ring of wealth affects how the rare drop table works. It removes most of the "empty" slots on the rare drop table. Therefore, the odds of receiving items is increased. A ring of wealth does not affect how often the rare drop table is accessed. So, when wearing a ring of wealth, the rare drop table will not be triggered more often, but when it is triggered, the player is more likely to receive an item."
I know it is quite a list in the wiki link, but for a scripting pro like you it should be easy to add, would be awesome for all your script users that are currently missing out on these drops.