Great Mothers cannot defeat Kelleran Beq

Was using Great Mothers, Morgan Elsbeth, and Nightsister Spirit in 3v3 GAC against a team lead by omicron Kelleran Beq, Temple Guard and Jocasta Nu. Once the battle was down to just Kelleran Beq I was forced to Doom him using Great Mothers. After that I could not defeat him. I think the game thought he still had his protection, even though it was gone. I hit him for 3 minutes straight and then had to time out my battle. Extremely frustrated that this happened and will likely cost me my matchup now.