Not to imply these answers are the best--they're the best I got at the moment.
I was at the game where the pirate who played CD well brought in a low level pirate and he soon said he noticed he just wasn't as good as he wanted to be.
Afterwards we discussed the placement of points on cannon items to improve one's performance at CD.
most important -- points on Shoot
2nd most important -- points on Rapid Fire
3rd most important -- points on Round Shot
4th most important -- points on Barrage
The use of a ram for improving round shot also helps your performance in CD.
