Their departures followed the exits of Bobby Zamora, Andy Johnson and Danny Murphy.
Jol said: "After Dempsey and Dembele left, everyone here was in denial and suffering depression, and we needed three days to get out of it. I was worried about the future. But then Berbatov began to show what a great capture he has been and how much he has influenced the side.
"He has shown his quality and helped us settle."