RKs do need to farm for their runes as the Rune dealer only sell the basics
Biosphere dungeons drop majority of the Rune Materials aside from Blue Hair, which arguably is an easier thing to farm than Anolian Skins since you need 20 Skins for an average of 5 Pyrexias, as compared to RK where you only need 1 Blue Hair and Claw of Desert Wolf for 1-3 Runestones. In terms of farm to materials conversion, it's very efficient for them at the very least since every mat they loot is already one piece of Rune.
WS/Mechas need to do it too, for their FAW/ABR machine.
Oridecon Hammers and Mini Furnaces can be bought from the NPC in geffen, (geffen_in 110, 172) for the ABR Capsules.
Steels and Irons can be bought from Para Market (paramk 49, 103) for the FAW Machines.
Even Biolos still need to farm for their herbs/seeds/plant bottle (not to mention their buffing potions, most of which need unsold materials).
Herbs can be bought from the NPC in Para Market (paramk 75, 102) for Red/Blue Herb Activators
Seeds are easily farmable with Harvester Hat, and they can be bought from @ws very easily too.
Heck, you could even throw Acolytes in there, with their holy water (that one is low effort farm tho).
Come on, Holy Waters are sold in Tool Dealers xDD
