I've noticed that the Join/Leave messages for players moving in and out of the zone you'e in really don't do much for the game besides add packet traffic and bandwidth usage, spam up the local chat messages, and produce annoyingly-loud sound effects when a lot of people zone in and out while you're loading into a zone.
If removing them entirely seems impractical, perhaps you could limit them only to people on your friends list? I wouldn't mind knowing when a friend of mine pops into the same zone as I am, but if someone I don't know at all just hops into the zone and immediately leaves through another signpost, that's two messages clogging up my local chat that I would've been just as happy withoutt.