I think dragon knight is an excellent pvp class. It has high damage, high survivability, and will work best paired with a healer. The class has no get out of jail free card like sorcerror (bolt escape) or nightblade (shadow cloak, consuming shadows). This means that if you build a squishy dragon knight, be prepared to die fighting if you get overwhelmed. This makes having a healer even more important, DK's are built to take damage in the face rather than avoid it, its a tank class. This is further evidenced by skills like spiked armor and obsidian shield. I think the class will work best in pvp as a tanky damage dealer, also called a bruiser. Pure tanks are always bad in PVP because they just get ignored and contribute very little to the fight, but a bruiser contributes a lot of damage and causes a lot of disruption with AOE CC abilities. The strongest pvp abilities look to be fiery grip (pulling enemies to bad locations), and searing strike (massive damage for very little mana cost). Ash cloud and dark talons are excellent AOE CC abilities that will greatly impact group fights as well. This will probably be one of the strongest classes to combo with a healer and contribute greatly to group fights.