The new dungeon, Ruins of Lordaeron, has a gather quest involving 25 limbs. Every party member had no problem completing this quest in 1 run.
The old dungeon, Wailing Caverns, has a gather quest involving 20 deviate hides. Most part members were lucky to get maybe 10/20 in 1 run. I have heard the same is happening for quests in Blackfathom Deeps for brainstems and pendants.
If the intent is to have people only run a dungeon once, as experience from killing mobs in dungeons has been decreased, please adjust the drop rates of items like these in the old dungeons so everyone can complete the quest in 1 run.