I would not only boost dungeon xp, but also hand out bonus xp when you run a dungeon with people from your server, and some other reward for running level50 dungeons with people from your own server. This would greatly improve the community on every server, while not taking away anything from anybody.

I also agree that FATEs need to be changed so that they encourage social behaviour (like chatting) more. Even after such a change they should not give out more xp than running a dungeon.