This exploit allows for up to 14 people to be in a single GvG team (though the above picture only shows 9 in Torment). It works anywhere, but is constrained (slightly) by the maximum party size of the zone. Urgoz/The Deep can have up to 21 party members, while areas with 4 or 6 party size limit have less maximum possible players.
What you need to do is compile a full team of 8 players (no heroes). Players A and B need to have NF, and thus the ability to add heroes.
All players but A must be able to intentionally load zones slow. There are a few ways to do this - one being to delete/rename your GW.dat file (not recommended), run memory intensive programs at higher priority then GW, throttle the connection allowed between client and server, etc. How you do it is up to you.
Everyone in the party (but Player A) must force themselves to slow-load. The party leader zones to a new area. Player A loads first, and adds 3 heroes while the rest of the team is waiting. After a predetermined number of seconds, Player B allows himself to connect. He then adds an additional three heroes. The party size is now 8/8 with 6 people waiting to connect.
The remaining players then allow themselves to reconnect, at a predetermined time. 14/8 party size.
I use Player A as you do not need to have a specific party position in order to add heroes.
Proof of concept included, 9/8:
http://www.angelfire.com/planet/salience/submitted/index.album?i=0