The guild packet stuff changed at some point, and I reworked it to make it work again. They're no longer sending the global list. Instead (unless they changed it again since I last looked at it), when you zone in, they send a list of guilds with members in the zone, and then if someone else zones in from a guild not in that list, they send a packet with that player's guild.
Newby usually doesn't include these opcodes in his updates, but looking at the binary, I think the current values should be
OP_GuildsInZoneList 5f77
OP_NewGuildInZone 5fbb
Though I haven't verified via packet logs that these are correct.
Edit: Also, regarding the numbering - the guild update packets include a constant that only seemed to be different if you're on a different server. So I assumed it was some sort of server ID or something. You wouldn't think it would be necessary except to support something like cross-server guild chat. So I assume there's some legacy reason for it - maybe because of something to do with the guild management backend. (back in the day, did server names used to have to be unique across all servers?)