Yes, I was getting the same error. I found that if I install the BPMN 2.0 Model Editor first then the missing dependency is resolved.
<http://wiki.eclipse.org/MDT-BPMN2 model editing tools>
The nightly update site is <http://hudson.eclipse.org/hudson/job/bpmn2-nightly/ws/org.eclipse.bpmn2.site/target/site>.
Steve.