1200 a bomb is a little decieving. I've sent 5 up to a building with just 4500 health and didn't kill it with 5. I think in the end it really does about 750 once armor/regen/whatever else enters the equation. Either way, a group of 15-20 of these things can reeeeeeally annoy. You have no idea how much you'll piss someone off if you take out their novalith with this ability.
The drawback is it takes 10 min for the ability to be usable again. Scuttle 'em and you can make them again, though the problem is they take so much time to micromanage that you shouldn't use this too much. It's a great way to annoy or distract your opponent, or even buy yourself time.
P.S. : If you want to piss off an Advent, take out his weapons labs. They put a lot of work into getting those. It hurts to lose them.
P.S.S. : To piss off a Vasari, destroy phase gates, or imperial/weapons labs, depending on which way they're going