If you're pulling the data from the same source and setting the query parameter (EmployeeName) before calling the data connection, then what you are describing should work. So, to be clear, the rules should be:
1. When Dropdown1 is not blank, use the Employee Name selected in dropdown1 to query the data connection, and return the numerous fields, and set their values in the main DOM.
2. When Dropdown2 is not blank, use the Employee Name selected in dropdown2 to query the data connection, and return one field, and set its value in the main DOM.
However, adding a second data connection, even as a troubleshooting step to figure out what's wrong, shouldn't hurt.