Millen told BBC Radio Bristol: "They are working hard. Their movement is good and we have the players to pick them out."
The win lifts City above Barnsley to 12th in the Championship table.
Maynard has now moved to 15 goals for the season, with only Cardiff's Peter Whittingham having scored more in the second tier of English football.
"Playing with Nicky is a luxury," said Haynes of the former Crewe man.
"At the start of the season we were partnered together and it is great to have that link-up again."
Source: BBC Sport
Source: BBC Sport