I've read that guide but when I launch the game after doing all the steps there is no offline mode. Just a "login" and "cancel" which throws me back at the "Press button to start the game" screen.
Blocking the game in firewall does nothing
Pluging out my network cable does nothing
Starting steam in offline mode does nothing
Every time I start the game it wants a connection to their servers. In the game there are "solo" missions yes like you can do missions in MMOs by yourself. But thats not a singleplayer. The game needs online connection and after pressing the play button there are several other human characters jumping around in the world. This is an MMO.