More and more MMOs are attempting to incorporate open-world content into their games. However, participating in open-world content often conflicts with queuing for formal instance-based group content.
For example, in FFXIV, a dragoon signs up for a dungeon queue that will take 20 min. While waiting, the dragoon participates in FATES in the open world. But the dragoon cannot join a local group working on FATES without conflicting with the queue. This is true even though such FATE groups are very transient in nature. People join and leave such groups fairly often.
The major issue here is the nature of a formal group in most games is very rigid. Once you join a group, the entire group signs up for queues, participates in content as a unit. This type of group is a little too rigid for open-world content that is continuous and on-going, with no real defined start and end.
Consider a world PvP battle like Tarren Mill-Southshore in the old days. Wouldn't it be nice to be able to join up with a group to participate in the battle, but still be able to sign up for dungeons and battlegrounds? Your queue pops, and you simply leave the open-world group.
Essentially, we need a new, more transient group type (maybe called a skirmish?) that only exists in the world. The skirmish cannot sign up for queues, but individuals in the skirmish can do so. Maybe everyone can invite people to the skirmish, or other people can automatically join the skirmish without needing an invite. The skirmish becomes the default form of group for open-world content. The more formal "group" and raid are reserved for explicit teams, or instanced content.