Well you may have just not fought a really good Antagonist yet. Antagonist requires you to know each char's strengths and weaknesses, how each mission works, how to read your opponents in melee with the RPS mechanics, when to push with the AI or pullback, etc.
It takes practice for players to learn how to play that role. I love doing it and have succeeded a number of times in the past, and lost a fair amount too. Haven't done any this weekend yet though.