One way to increase party play would be to add benefits for doing the now soloable content in a party.

EG. when doing salvage in a group, all NMs drop a guaranteed cotton purse to all members in the party, and the end boss has a chance to drop a linen to all players as well.

In Dynamis, all NMs drop a guaranteed 100 piece to all members in a party, while the zone boss has a chance to drop 2 to all members.

Sure, there are people with multiple accounts that would abuse this feature, but on the whole it would improve this game. There's currently no reason to team up to do these events as they're all soloable and you get more money from doing it solo.

Other benefits would also include reducing the stress on salvage zones, as there would be more people doing it in groups instead of all trying to enter their own instances.