When I say I'm not missing this is what it looks like...

[The Mighty Gerbil]

I do miss legitimately, like with some of the Ambassador shots in the video, but with the stabs I don't think so.
http://www.youtube.com/watch?v=tQlnAPsZy_A

 

[toj-Grey]

At first I thought maybe you meant that something was fixed or removed from gameplay, but you are stating that your bullets missed their mark but that doesn't mean that the knife backstabs should too.
I'd agree with you there, you had two and a half good seconds of clean stabs to the back and the hits didn't count has crits, Valve is surely making a quality product.