David Rainey found the net twice as Crusaders scored three second-half goals to keep up their pursuit of league leaders Cliftonville.
Mark Miskimmin missed a good chance for the home side early in the second half but Rainey fired past John Connolly on 52 after some DC defensive indecision.
Timmy Adamson grabbed the sceond after 55, finishing in style after picking up the ball at the edge of the area.
Rainey made it 3-0 with his second strike in the final minute of the game.
Chris Morrow had a good early chance for the Crues but he fluffed his shot wide with the goal at his mercy.
Yohann Lacroix saved from a Sean Cleary overhead effort and Matthew Snoddy saw his attempt pushed away for a corner.
The match sprang into life after the break and Stephen Baxter's team remain nine points behind their north Belfast rivals in the Premiership.