I got an idea for an interesting use for firedragons. These are described as a sort of jack-in-the-box tank-popping unit and I thought that if used differently they can throw your opponent right off. Imagine for a second: 6 FD with exarch who wields the Dragonsbreath and has crackshot. This makes for a S5, autohit, reroll wounds, and AP3 weapon backed by 5 melta shots. Your opponent thinks of this unit as a danger to his tanks and may make a mistake with his infantry. I'm pretty sure most 10-man Space-marine squads will die to this even in cover unless deployed in a funny way. If any are left the Serpent can add some Shuri Cannon fire. Anybody tried this? Thoughts?