Sorry for the late reply. W doesn't slow down enemy AS anymore and it only improves allied AS not your own, thus taking it so late as it doesn't offer any real benefits until late game.

Why take W so late? the AS Reduction can be useful, also AS Improve for teammates + yourself

Thanks man I tried out this build and it works amazingly, the early game can be rough but mid to late I just have so much sustained damage with that cdr, keep up the good work... Loved this guide... thumbs up all the way