I have noticed something, and I may be wrong or jst bad RNG, but drops from nodes are not always the same. What I mean nodes in different zones drop different range of things.
The iron nodes in Windsward drop lower/lesser items than the iron nodes in Brightwood or Shattered Mountains. it seems more noticable on orichalcum, mined alot in Mourningdale and on very very rare occasions gotten something extra, but in Shattered Mountains I consistanly get more/better drops, noticed this in foraging also.
May just be me.