Kimbra and Jessie J just have voices that are similar to Katy's, I mean you are making my point for me. Her voice/material is not distinctive. Domino could have been sung by anyone.
As to Katy being distinctive Pop/Rock Avril, Kelly and P!nk are way more distinctive pop-rockers then Katy is as of now. I would say the Katy Perry of 2008 did have a signature sound, Teenage Dream Katy doesn't.
Primadonna does not sound like a Katy song
