So I'm having a problem right now. I have vanish no packet installed and everything is working, except for one feature. And that is hiding users off the /list list.
They still show up for all players even if they don't have vanish.see.
They disappear off the tab list without trouble though.

I have essentials that handles the /list.
I use this version of vanishnopacket http://addons.cursecdn.com/files/787/504/VanishNoPacket.jar

I don't know what version it is exactly.
I use groupmanager for permissions

There may be an issue with Essentials. I've been seeing a lot of these reports. Will look into it soon.