As I understand it...
The Directory Service Query Tool is used to query Active Directory (via LDAP) to return users and groups to create access accounts to use LEM.
The Directory Service Log Connector is used to query the AD logs to return event data.
As far as I know there's no crossover between either. You use the DSQT if you need to create AD-based LEM accounts. You use the DSLC to get AD-specific log data.