Just to be clear,
You don't need the NCSoft launcher for demorecord playback at all, it only needs the CoH folder.
<installfolder>\cityofheroes.exe -demoplay <some.cohdemo>
Btw, if you make a shortcut for "<installfolder>\cityofheroes.exe -demoplay", you can drag n drop any .cohdemo file onto it to play it, instead of rigging individual ones per demo (or using the command line).