I think, that filtering options are very limited for users, because they cannot simply create complex search options. Users need to create options such as selecting requests which status is equal to "Resolved" or "closed" etc. Or they cannot choose filter where value "is not equal to"...
All they can do is selecting one option per field.
Solution would be posibility to select more options per one field and to choose the operands (is equal, is not equal, OR, AND).
I know that they can create complex conditions by typing the field name, valu etc., but it is not usable for users, because they do not know the field names and syntax.