Is RNG a bit busted?

I've noticed that depending on the character I play, I get vastly different drops. IE, my lvl72 Monk rarely ever gets Iron Rune drops. And I mean rarely. Ever since the OG Act 2 -> endgame/maps, I've literally only had 3 drop. And I have an abundance of every other rune.

Yet if I go and start playing another class/character, I'll get them to drop like candy.

Now Im starting to notice/wonder about this during the endgame. Im primarily playing my Monk character, and I've slotted in gold Tier 1 waystones with 245% waystone drop modifiers, using 2 Precursor tablets on two different towers with boons saying "xx% increased quantity of waystones found", while also choosing the "Higher Tier Waystones" in the Atlas Tree.

Just ran three of those stacked maps and I had (4) basic Tier 1 waystones drop... So at this point, Im not sure what Im supposed to do to start getting Tier 2+ waystones.