So I figured it out... the hornetq messaging stuff is missing from the standalone.xml and when I used the standalone-full.xml the jbpm configuration (datasource, etc. ) was missing. So I had to patch the standalone.xml file with the messaging module. I have created a gist with the patched file: maybe that can help someone save some time :)
https://gist.github.com/herwix/6166792
You have to replace the standalone-as-7.1.1.Final.xml in the jbpm-installer directory and reinstall the demo or just patch the standalone.xml in JBOSS_HOME/standalone/configuration, however, this file will be overriden with standalone-as-7.1.1.Final.xml if you install the demo again. So make sure to patch that file as well.
Cheers, Alex