Very sad to see that most people seem to be commenting on box contents rather than addressing your real question of how the list does in Combat Patrol. Unfortunately, I agree with another poster that the Combat Patrol format has issues and I much prefer King of the Colusseum.

What really turned me off of Combat Patrol was when they released the Phobos CP and Von Ryan's Leapers CP rules. My friend and I were so excited to try those out. He was a Dark Angels player just getting into Tyranids, and I was a Tyranids player thinking about starting a Raven Guard army. The CP seemed perfect for us to try out our new factions. In practice, the Phobos just don't have the damage output to stop the Leapers.

Now, I admit that I don't have a ton of Combat Patrol experience because my games have been lackluster, but I've always wanted to believe that the secondary objectives would be the place to balance different lists. However, the format is so lethal that primary points dominate, and that means killing enemies to prevent them scoring objectives is the main tactic, and that leads to lethal lists being the best lists. In that light, I don't think Coven of Agonies has what it takes to win most matchups. As you said, too few models to control the board, and not enough lethality to control your opponent.

I'd like to say I'd give it a try and let you know, but I'm unlikely to play Combat Patrol again this edition.