In the previous output that you posted (now deleted), adinfo --diag showed many environmental issues around DNS and unreachable Domain controllers. Have those been fixed?
Also, is this a very large AD environment? Remember that the Express method (Auto Zone) does have limits; the behaviour you are describing sounds like adclient is talking time to build the cache which is expected if you have a large environment; that is why for commercial organizations, Standard Edition is the way to go.