Black Cleaver on zed? And My build

So ive noticed all the build guides on zed have black cleaver on them. I can see why it would be good on zed, decent ad(50) great cdr(20%) and 300 health which any champ can use. But I feel the main point on black cleaver is the armor shred. And to optimize it fully you need to get 6 attacks or spells off, but as zed you aren't really auto attacking more than once or twice per combo, so my question is is it really worth it on zed. Also the Ms is nice, but unless the enemy flashes away I don't usually have a problem sticking to targets.

My Normal build is Usually maw, since I'm against ap, then ghostblade, 1st if not against ap. then Deaths Dance. then duskblade. That's my core. IT gives very high ad, great Lethality which works well with duskblade. and 30%cdr. And good life steal. Then situationally either BORK, or maybe mercurial scimitar if a lot of ap, or LDR if they have a lot of armor. And boots depend on my runes I take, if I take my page that gets me 10 cdr I take merc treads. If I take a different page, I take lucidity To get me to 45% cdr. Any suggestions, should I be incorporating black cleaver into this build?