A simple Diadem possible Fix

Improve the objectives system. Incentive/Force people to explore and collaborate.

Make 3 chained sets of objectives, each having harder difficulty than the previous one. To progress to the next one, you have to complete the whole list.

SET 1:
Slightly quicker to complete than the current one, requiring both battle (involving 1-2 rank mobs) gathering and exploring actions.
Rewards with 3 bronze coffers.

SET 2:
Same as the first but requires to kill rank 3-4 mobs. One objective will require gatherers to gather a semi-rare map that will spot the location of an item to retrieve to complete the objective.
Rewards with 2 Silver coffers and spawns a NM in a random location of the map.

SET 3:
Involves Vs, a NM and caves in some cool way. Rewards with 1 gold coffer and spawns a NM in a random location of the map.

NOTE: Coffers do NOT drop from ANY mob until the group has completed the third set. Only the mobs required in the objectives may drop coffers.