I have 5 characters, and done this quest 3 times now hoping the drop rate would be better (come on blizz, pull the thumb out ur ass!!) but sad to say it is the same, killed over 100 elemental's for 7 core's this time (u might be lucky and get them quick, but if after 10-15 kills u only have 1 core, drop this quest and move on!! unless u love farming, boring, boring, boring.)
DO NOT GO NEAR THIS QUEST!! it's a waste of time..