Using GNU Emacs 24.4 on Windows.
Can't get autocompletion for vibe.d package even for "empty project", just "dub init" with vibe.d in AppData/Roaming/dub. Autocompletion for std works great! (after dcd.conf file in $HOME/dcd.conf).
You have to edit your dcd.conf
file and add every folder of the vibe repository that contains some *.d sources:
then restart DCD-server.