In the meantime we were able to get it runnign with AD LDS. It just required some minor tweak in the schema. So far so good, but i stumbled over one thing. When importing users to vcloud director the LDAP search limits the results to the OU defined by the system administrator. But when importing groups, all groups from the whole directory are visible. I would not call it unsecure, but at least it leaks out some information.
I doubt that it is because of AD LDS. Can someone confirm the behaviour with a "regular" Active Directory ?