Reign of Gaming

As Scarra said in his Stream today it doesnt increase Ahri's true damage. Though i am not sure if it's intentionally programmed like that or a bug. And I can't tell if he's right since even pro's can do mistakes.

I am following this site for quite a while now and i've seen some threads about vayne but my question doesnt get answered in any of these threads.

Basically my question is wether Trinity Force is viable on Vayne instead of a second Phantom Dancer or not. I've seen some streams where pros tried it and i want to know if they were trolling or there is a reason behind it ( the tried TF on MF too so i have a reason to think they were trolling xD )

So I'm playing Vayne a lot at the moment and thought about playing her with Trinity Force.

My usual build goes for BT and PD first, followed up with an defensive item. With Boots i have 4 items at this point in the game and most of the time it ends around there cause either i am fed and the opponents surrender or the enemies are hardly fed and my team surrenders. In rare scenarios our teams are on par and i can buy 2 more items. I can decide between getting IE, Mercurial Scimitar, LW and/or a second PD. I take Mercurial of course if the enemy team has surpress or much cc. But in other Scenarios i go for IE and then PD and ignoring LW since Vayne doesnt need it.

Now i was thinking of buying Trinity Force instead of a second PD because i already have the ''unit collision'' passive from PD, Trinity gives more %MS (easier kiting) and furthermore some HP (cause Vayne is too squishy), a Slow (same as %MS, easier kiting) and the Sheen procs. So my question is does it make sense to go for Trinity or does a second PD beat it easily because of the higher crit chance and AS buff?

Sorry for bad english, it's not my native language.

pls no comments like ''you wont get there anyway'' that's not what this post is about.