Most important part of the setup is for a Xerox device, the Search Directory Root, Get that wrong, or don't use it, and it will almost always fail. No idea why. Also, for something and giggles, switch between ADS and Exchange and see if it works
If using Exchange, Swap port to 3268 (global catalogue port) supports larger packet size and has longer time-out.
Try (|(sn=LDAP*)(cn=LDAP*)) in the custom filters
Been unable to get LDAp top work on any of the xerox systems we haev here at the office , some of the postings are old on the sites.
We recently had the 7530 crash and had a tech onsite to reinstall the system. I haev checked all configuration and still no go.
If there is some document I have not come across let me know.