User blog comment:Deshiba/Circumventing armor for marksmen/@comment-6061249-20150520133147

Having long cooldowns on abilities doesn't exactly mean it's worth to purchase CDR. See: Draven, Gnar, Yasuo, and few more.

Basically, you can trick around CDR there, but... Isn't it just better to get straight onto the core of your job? Why would you use CDR instead of doing an average build for ADCs which will make you deal enough damage to forget about your cooldowns?

Rage passive is also something you don't need. Damn it, Ashe was already awfully strong at slowing enemies, and now is even better (which is exactly opposite to what Riot claims they want to do - remove permaslows). Rage, on top of that, is just an overkill. At emergency situations, you should throw in your ultimate which will successfully remove any problems with kiting.

The only things that shine on this item, besides of AD, are the armor penetration and to some extent health. You'd be better with having instant damage, but sharing the penetration is a considerable thing. And the health, might make a difference between getting slain and staying alive.

In overall - just pick up Last Whisper.