I have correctly setup views to work for civicrm fields and am also using the civicrm entity module for Drupal to expose fields. In my testing it seems like the custom fields work for certain types of civicrm components. For example, if i use a custom field for All Contact Types then it works correctly and even the dropdown shows CiviCRM:Custom - Field name. However, for a custom field for Cases it does not work and has the same issue i.e. refers to SQLSTATE[42S22]: Column not found: 1054 Unknown column 'civicrm_case.custom_3' in 'field list'. Has anyone had any success in using custom civicrm case fields in Drupal views?
I spent some time on the setup of the Views and it does actually work. However, what is missing is the relationship in the View. It is subject to the type of view you try to create and the relationships. Also remember to choose the CiviCRM Custom: [Field_name] instead of the one provided by CiviCRM Entities.