SE please make an announcement because somehow it is not clear enough in your ToS. Greifing by way of not rolling on loot until the last seconds is not allowed.

The Idea behind this sort of greifing is that players will become frustrated and leave the instance thus no longer being eligible for the loot thereby reducing the amount of competing loot rolls against the greifer. Thereby forcing players to stand around for several minutes waiting after their legitimate roll for their loot.