Deathwing knights are probably the best melee terminators in the game by a fair margin. Landing 30 Deathwing in front of the enemy is pretty hard to handle.
In this game the Deathwing Knights only had an opportunity to fight a full health demon prince and a pair of obliterators. They killed the three models in one round of combat without trouble. They are very durable and the shield wall gives them a nice boost in that department.
Deployment.
Terminators arrive.
Swarmlord and a flying tyrant managed to wear down and kill one unit of ten terminators. The other unit of ten took a huge amount of damage to kill but the two together did so much damage the enemy couldn't recover. The knights also managed to kill a heavily wounded Barbed Hiradoule.
In the end I had the Azreal, Ezekial, Belial, the Deathwing Ancient, 6 knights out of 8, 15 of 20 helblasters, 10 devastators, and 11 of the 22. The army put out an oppressive amount of shooting and had plenty of multiwound models to soak up the attacks from the various giant monsters that survived the initial small arm shooting.