Guild Wars 2

I think that someone tried to fix several bugs tied to world events by making attacking mobs invulnerable before they reach certain destination.
This is very annoying.

Please if the mobs are not vulnerable, mark them somehow. Maybe introduce a new color for hostile and invulnerable mobs.

Many, many events were already like this. A good example is defense of the second beacon in the Melandru chain; the mobs that spawn are invulnerable until they reach the defense area (or for a few seconds if they spawn within it.)

This is to make sure that mobs for events are killed by people doing that event, instead of some randoms who happen to be over where the mobs spawn.