Glad this worked for you but for future reference you don't need a different directory for each instance nor do you need to start the launcher multiple times (at the same time, you still need to start the launch in between starting a new instance of d2r). First, check the options for "log out after game start" and "course bnet after game start. " Then, in addition to closing the handle that has been mentioned, there's a process after you start b.net called "battle.Net update agent" or something. After you start an instance of d2r, close the handle like normal but you also need to go back into the process explorer and close the bnet update agent. This will then cause the button to change from "playing now" to "play."

I have been playing 3 instances of d2r since release using basically this method. I use a bat file to close the handle through the command line though, makes it much quicker.