Yea. They actually come all the way back from table top games such as Mage Knights when they had the dials and your abilities had a dr on them and also could not damage for everyone in contact with your attack unless you had a special ability for it, so yea aoe and dr have existed since table top game way before WoW ever came out. It was created so that you couldn’t just have one random caster come onto the map with an aoe and use one spell and wipe out 200 people with one attack.