Returning to the Rebels for the 2011–12 WHL season, Dumba scored 20 goals and 57 points in 69 games. He was the youngest player invited to the selection camp for the 2012 World Junior Hockey Championship, however he failed to make the team. However, he continued to impress scouts and observers with his play. Don Hay was one of several WHL coaches to praise Dumba for his enthusiasm on the ice and hard-checking style: "He's a guy who can do all aspects of the game ... he's a very dynamic player with or without the puck. Yes, he can lay out a good bodycheck, but he can also score the overtime winning goal."