What was the last world event that you did? Did random players in the area just jump in, blow away the walker and leave with no fanfare? World events are meant to bring players together in one spontaneous and common goal. In my opinion (taken with a grain of salt) this experience is very lackluster.
If you want a model of how spontaneous world events should be run, look at Rift. Event pops up, players get a notification, quick invites are sent, and everybody works together to close the rift. It is extremely gratifying, and possibly the only thing I miss about that game.
So here it is.
World events lack player cohesion and motivation to participate.
Add a world event voice chat. A simple catalyst for human communication in an event can boost morale significantly. Players will be able to communicate with each other during a world event, coordinate against the threat, and collectively cheer when it is downed.
Add a prompt in the player hud when a world event is about to occur (60 seconds prior should suffice) in the area (200m radius?), which the player (or fireteam leader) can accept by bringing up the ghost HUD and opting-in. Event voice chat would continue for 1-2 minutes after downing the threat, or whenever the player opts-out of the chat.
Let me know what you think.