I'm questioning whether shadow warriors actually have 1/16 chance of accessing the rare drop table. A conservative estimate says I've killed 1000 in search of a tooth half of the crystal key. From the page on the RDT the chance is 19/128, so 128*16/19 < 108, and the drop chance is greater than 1/108.
Then (107/108)^1000 < 1/10964, a chance of 1 in nearly 11 thousand of no drop in 1000 kills. The source of 1/16 seems to be https://twitter.com/JagexAsh/status/635837312086220801 but here God Ash actually directly responds to "Do you mean the Rare drop table?" with "There's a gem drop table, used by most creatures that drop gems. The rare drop table is on it.".
It's also worth noting I saw none of
- 3k coins
- Loop half of key
- Runite Bar
- Silver ore
- Nature talisman
- Any rune+ weaponry / armour
Dropping one of these including the tooth half is a chance of atleast 71/128 according to the RDT page and so the chance of none in 1000 drops is less than 1/2^1000, which is tiny even accounting for me picking these items after my 1000 drops, and RNGesus chosing me from among the OSRS players.
But did see lots of uncut gems, including 1 diamond, atleast 5 rubies, and probably 30 gems overall. I also saw a few chaos talismans.
It seems possible this random drop table / gem drop table confusion is elsewhere too.