You do realize that the more players there are and difference levels form both player and mobs plays a huge role on how often they drop right?

Example: Solo same level 1-10 up to chain 30 , same level party 1-5

Mobs +4 levels above with out side interference 5-15 to chain 30.

IF your on the NM train they are extremely rare unless everyone in party is same level fighting mobs same level or higher.