Is Black Cleaver any good on Janna?

I was building it for damage in fights because I max W -> E -> Q.

And also because CDR. Offensive masteries CDR quints boots of Lucidity...... Black Cleaver seemed like the logical choice and trust me it feels really good. one thing i like to do is build a lot of attack speed so i can get the shreading going a lot faster. zephyr and trinity force are strong items because they give a lot of attack speed and also give movement speed to help you get in range because you have low range attacks. another trick i have up my sleeve when i play is i like to knock people up in the air and then attack them really fast before they hit the ground then blow them into the adc and have him clean the kill up lol haha. you can also use ur towers as a distraction then shield the tower while you shread their armor really fast then kill their creeps with a twister which makes the tower attack the person who has no armor and it kills them REALLY fast.