If the same reward can be achieved with lesser effort, people will generally always go for that method. Diadem by design does little to prevent this as there's little work beyond taking down HP sponges and dodging the occasional AOE. It being available through DF, which fuels an individualistic mentality among players as it is, just escalated the issue.

SE had FATEs and Hunts to see how players will react to something that can be mindlessly zerged given enough people, and yet they still implemented the same type of concept here.