The phrase 'dear member of staff' is correct and usable in written English. You could use it when writing a formal letter, for example: Dear Member of Staff, I am writing to report an incident that occurred yesterday evening...
The leadership, staff, and supporters of the American Committee for the Weizmann Institute of Science deeply mourn the passing of a most esteemed and dear member of our family, Professor Ephraim Katzir.
Today they lost a dear member of their family.
Dear athletes, dear members of the Olympic family.
Dear Members of Congress, Hi.
"Dear Members of Congress," reads one of the letters.
A member of staff strolled by.
Dear Members and Staff, I want to clarify a few things about Uber.
The entire Beth Israel Medical Center family joins with the physicians and staff of the Department of Radiology in acknowledging with sadness the passing of our dear friend and colleague, Jeaneatta Steed, a beloved member of the radiology staff for over 22 years.
The Jewish Museum's Volunteer Association and staff mourn the loss of our docent and dear friend, a beloved member of the Museum's family.
Only nine victims told members of staff.
Talk to new members of staff.
Ludwig does not simply clarify my doubts with English writing, it enlightens my writing with new possibilities
Simone Ivan Conte
Software Engineer at Adobe, UK