I've been seeing Vayne a bit more frequently and may consider moving her up despite her aggregate score. I do not believe her Defense/Utility should be increased any further, but I do agree that she is the strongest ranged AD in CS right now. What exactly does that mean in the context of overall team selection? I'm not too sure yet, since Vayne is also vulnerable to Hextech Sweeper, CC, and burst damage.
I'll be making changes to Yorick, definitely. He should be T2.
Master Yi is low tier because he is good for running around like a gypsy, and that's about it. His primary strength of being able to chase is more or less useless. Annie is low tier because she is reliant on Tibbers to drop on top of 3 of their champions, and is not very good at getting around the map. She is a strong caster and will make enemies think twice about initiating on a turret, but beyond that, she lacks the mobility and sustained throughput that many other casters offer.