Well I can't say the exact random values. The behaviour seems to indicate a result mechanism similar too this layout. Also keep in mind that diablo2 uses a layered percentage. So rolling could actually result in 2 drops. on the base kill rolling 10% would drop gold AND an item.
50% to drop gold
10% to drop item
90% for potion(random 50/50)
10% for gear
90% vender stuff
on magical(sorry, i don't recall the colour scheme)
10% super(very rare)
this results in an increase decelinitino of odds. Also in Diablo 2, items were unknown. The reason was that then they can spawn the stats when a "Identify" was used. The item had a base level(based on creature) ans the stats were pulled on the level scale.
obviously set pieces were a little different :)