How to Nerf Vayne Without Gutting
Remove the interaction for her Q's damage to critically strike. (To clarify for a few people, Q's damage gets added to her AAs after crit amplification is calculated, so when she autos with her Q it can still be a critical strike, but her Q damage itself won't have a crit amplification to boost itself before the Q and AA damage gets combine into the damage to be delt.) A ton of the damage people complain about comes from that 1 interaction. Removing that will make her much more balanced and far less frustrating without destroying her ability to be usable.