Basically I'm wondering if at full build if Last wispier or Shiv is better. Basically I'm wondering how much armor on your opponent makes LW better. I cant find any spreadsheets or anything that take her passive into account in regards to the AS on Shiv. Anyone figure this out?
Basic build order: BotRK --> Boots --> PD --> IE --> Def Item, Shiv, or LW depending on situation/
obviously there is variation of build path depending on the game but this is the average result.
I would assume that Last Whisper will be more consistent in most cases. A lot of your damage is physical through critical strikes, so they will typically do more damage than your Silver Bolts even to tanks.
If you really want more attack speed, it might be worth looking into getting a second Zeal item instead of Infinite Edge (Trinity Force, Statikk Shiv, or Phantom Dancer). I'm not sure how the numbers work out, but it might be worth looking into.
Of course, if the enemy team doesn't have many tanks (or you find you aren't having any trouble killing the tanks) you can just replace Last Whisper with a Phantom Dancer/Shatikk Shiv without much issue.
Long read, but with TL;DR: It's also about Kog'maw, but may be applicable to vayne.
http://www.reddit.com/r/leagueoflegends/comments/2a4end/last_whispers_last_whisper/
It's worth noting, however, that LW is pretty cheap compared to other items. So you almost always want to build it as your 3rd/4th item, over another AS/crit item, for the power spike.
