Sorry for late response, but I haven't visited the website in ages. I would update the guide but I stopped playing League a long while ago, so sorry 'bout not up-to-date guide.
I left it so people may still find useful information.
Cheers

Hello there again,
as I told you, I'm playing it because I like it and I'm used to it also it has quite much damage after the recent changes too.
Hope you enjoy your games with rushing Blade of the Ruined King :) If you have any further questions or doubts about what to build, etc. go ahead and ask!

I'm glad you're asking. I stand it because... I'm just used to it...

It was quite a weaker item pick before, but now, since they buffed it - it's a "must pick" pick, in my opinion. Percentage health damage is, well, a lot now.
You will most likely get a B. F. Sword after first back for the flat AD anyway or Zeal for the Crit damage - that's what most of the people did and will do.
In this build I show that rushing Blade of the Ruined King as first item is usually a good idea. It gives you everything you need(apart from Crits...)AS, a little bit of AD, lifesteal and %HP damage. It also gives you 10% max enemy health damage on Active Use, heals for the same amount + 25% of targets Movement Speed, which is really helpful in fights.
Rushing BOTRK along with Warlord's bloodlust gives you insane sustain on your early laning phase, in which Vayne mostly falls back from other ADCs - so all you have to do is survive early and after these 20 minutes you can get your power spike after Phantom Dancer or Statikk Shiv or whatever you build then. Also if you're playing properly in the laning phase, trades can be really easy - you can just go for a few hits (3-4) and after you lose some HP from that you can just lifesteal from minions and so the trade is yours. It's not the same with Statikk Shiv for example, because then, when you trade and lose health you're most likely going to be low health for a long time, that means you're vulnerable for further trading. It indeed has a lack of Crit, but I think it's a really good choice for Vayne as the first item.

It's quite a personal preference I think - some prefer Blade of the Ruined King, some Phantom Dancer, some Statikk Shiv and some even Infinity Edge. If you like rushing other items as first, go ahead, it's up to you, although I would still recommend to get BOTRK as a second/third item.

If you have any further questions, opinions, doubts or other observations/notices - ask ahead! I will do my best to answer :)

Hey there!
The build works really well when you're fed, as you are in the video(good job with the penta, btw!)and enemy doesn't really have many tanks.
There's a tip for late game when you go for Phantom Dancer, Statikk Shiv and Duskblade of Draktharr - since all these items give movement speed bonus you can go ahead and sell your boots for Rapid Firecannon for example - which also gives a small amount of bonus movement speed. All of it, combined with your Night Hunter and Final Hour gives you really good mobility(also you have 100% Critical Chance with these items)
So you should try that in your future games and let me know how it goes for you! :)

Thanks for your opinion! Any advice on the guide is appreciated and I will surely take it into reconsideration and add some more visuals.
EDIT: I added some gifs and other pictures to the content! I will add more in the future as I gather more information and materials! :)

Thanks man! I'm working quite hard to make it look at least OK.

Hello there!

First of all thank you for checking out my guide and taking your time to write a comment!

Now, let's go straight to the topic:
I have been always maxing Q, even though I picked AS Quints(which I pick becuase Vayne's Attack Speed in early feels really low) and that's because of the weak early laning phase. You're most likely going to get counter picked(if ranked), so champions like Corki, Draven, etc. and while playing against them maxing W is pointless, because you need more hits to trigger your Silver Bolts, so longer fights with them will lead to your death because of their higher damage output. Tumble, however, gives you farming potential and mobility, so if you're laning against someone like Draven, Corki or Caitlyn it's really helpful to get the CS.
Also, this meta(after Q buff) you most likely get B.F. Sword after first back, which I forgot to mention in this guide for some reason lol, and you get the AD you were missing from runes and gain more damage from Tumble, while still having high AS from runes :)
Although, I think you can still go for Maxing W first, it's still good and most likely personal preference and based on match-up!

I hope I explained at least some of my way of thinking... if you have any further questions, I'm here to answer them!
EDIT: Because of the incoming nerf to Vayne in further patches, I think maxing W would be a good idea too!