Must instant kill leader in GAC

When I reached tier 4, I thought it might just be part of the tier but I’ve come to find out that I have to kill the leader in order to win the match.   Each team I’ve been having to instant kill the leader in order to win. Now I’m in tier 5  and I’m trying to beat a team with hung and and they get the team down to no health and yet the other toons are not dying and I can’t kill anyone. Seems to be a really bad error on EAs part in the Game.