Bit off topic.
I once built a group of scouts, and sent them to an enemy planet. Once my scouts arrived, I fired a total of 68 Kostura cannons on that planet.
This was against an advent AI set on unfair btw, and he had mustered an large army there.
Back to the planet. Everything died, except the starbase. I think it had about 40% shields left and 100% hull.
You can get the same effect with about 7 shots I think. Starbases are pretty much impossible to kill with a Kostura, but you can get rid of all the crap that is preventing you from killing the starbase. 
Using the deliverance to 'kill' a planet requires 2 deliverance engines and a number of bombardments, its best not to condsider it outside its main role of fleet buff gun because culture killing is not something that happens quickly (or often) enough to effect with a 1 click ability.
I think it is a pretty handy to "culture kill" worlds with the Deliverance engine if someone is dug in at their last couple worlds. No reason not to use the full capability of the weapon if the opportunity presents itself against a world with weak culture.
I was kind of disappointed when I discovered Novaliths could no longer do this, considering there are a number of people who like to waste time by holding out at their HW as long as possible when the game is pretty much over.
