Questions about Fiora and Vayne.

I know that Fiora has been considered strong(maybe not now) due to mainly her percent health true damage, a short CD dash, and an ultimate that gives lots of heal, so people have been wanting to nerf her. My question is that if people think she's op, then what about Vayne? I compared Fiora and Vayne's stats on lolwiki, and it seems to me that they are very similar and Vayne is even stronger? Here are my reasons:

1. With max CDR, Fiora's Q has a 3s CD(when it hits an opponent), while Vayne's has 2s; both of which have short distances. Both of them deal percent health true damage, but Fiora needs some AD to reach 12% while Vayne doesn't need to build AD to reach 12%. Vayne needs attack speed for her W, and when she has BORK, boots, PD, it seems easy to land 3 AAs in 3s(and this is Fiora's Q CD). Vayne only needs AA to deal percent health true damage, but Fiora needs Q, getting into melee range, and some positioning to do the same thing.
2. Fiora gets movement speed bonus only when she proc the passive or when using ult while Vayne only needs to be around her opponents and Vayne is ranged, and her ult gives more. So Fiora can stick to her opponents easily while Vayne can kite her opponents easily(even more easily?). These 2 seem to negate each other to me.
3. Fiora's ult can be cancelled by a QSS while Vayne's can't.
4. Fiora's W, her only CC, has a longer CD than Vayne's E. While Fiora's W can negate hard CC, it can only be used in a reactive way or with lucky prediction, and I think it's hard to react to Vayne's E due to the short start-up animation. My question is why Fiora has been considered one of the strongest top lane champions since the end of last season while Vayne hasn't? Why is Vayne not played in the top lane like Fiora in pro plays? Is Vayne stronger?

PS: I started playing LOL at the end of last season so this post may look very stupid to you.