AS blues are one of the best blues you can go for if you're doing damage. They are actually really really good on junglers, the problem is just that most junglers cannot afford to give up MR.
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i was being a little bit "too" generic regarding ArP reds - Kog'maw as an example is probably better with something else. But he is weird.
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re: Vayne's W
Tumble is an autoattack reset (auto > Q > auto) applies 2 stacks really fast and isn't affected by AS since the reset.
Condemn also applies a "ring" so auto > Q > auto > E is the best burst Vayne has for quick trades (and pushes the opponent away so that they can't counter).
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re: AS as a dps increase versus other marks
AS reds only improve autoattacks. AD/ArP improves autoattacks as well as abilities (unless you're Kog).
AS reds only have very specific increases in damage if it isn't a very prolonged engagement.
It's a piecewise function.
As you can see, you increase you damage for brief parts of a second, then your opponent "catches up".
That graph was assuming a default attack speed of 1 second, and a 10% AS boost. The exact numbers don't really matter - they will all look the same. Higher % increases will obviously converge faster to their "true" value.
That function is also comparing to someone no red runes, no abilities, no ignite, no repositioning.
AD/ArP runes are stronger with abilities, Ignite allows for "overkill" where very small increases in damage end up not mattering, and AS runes lose more damage to positioning.
To clarify, between the .9 and 1.0 second you have double the damage, because you autoattacked twice when they haven't yet. However, between the 1.0 and 1.8 second, you both have done the exact same amount of autos, so there is no damage difference. 1.8 - 2.0 seconds, you have auto'd 3 times, but they have only done it 2 times. So you're 50% ahead. Then they autoattack a third time and you are equal again.
This graph gets a lot more sad against people with actual runes.
You start out behind (at the 0 second mark when you both auto'd, their auto hurt more).
At the .9 - 1.0 second, you have like a 90% increase in damage. However, when they get their second auto, they are ahead from 1.0 - 1.8.
Then you pass at 1.8, so you're say, 40% ahead. Oh, but they catch up at the 2.0. Now you're behind again.
2.7, you pass again. Say, 28%. Then at 3.0, they are ahead again.
Abilities make this even brutal.
TL;DR: Vampiric Scepter + 2x Doran's Blade = noob trap. Build literally anything but that.
is a really really really really really really bad conclusion.
They are evaluating damage only against a 100% stationary target. THEY AREN'T EVEN CONSIDERING ArPen. THEY ARE SAYING LIKE IT DOES NO DAMAGE. LIKE YOU DONT EVEN HAVE RUNES.
They are giving ZERO benefit for the hp the Dorans give, and the Lifesteal. They are also using a "punctuated autoattack" approach like me (eg, a piecewise function).
The difference is instead of comparing the piecewise functions to each other, they are comparing it against an extremely arbitrary target. TTK AGAINST AN ARBITRARY TARGET IS A REALLY STUPID WAY TO COMPARE DPS VALUES. This is because of the nature of piecewise functions.
They are saying "oh it takes 16 autoattacks to kill this random target". That isn't a good way to do it.
Now, this sort of piecewise math requires like advanced calculus and shit when it comes to comparing it against eachother.
And ArPen is really difficult to measure because it doesn't increase your raw numbers as much as AD, but what it does do is reduce the effective hp of the target, so you have to do less damage to kill.
A better way to compare ArP/no ArP is "% of effective hp done per second". That's a lot of work.
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Now, i agree that it is a weaker build because it takes so long to get going. But Blade + Vamp isn't a weak build.