I just think #3 fits in-line with the design of her Ultimate (transforming her original kit) & with the motif (being on the hunt or having a keen eye). It's very unnecessary, I just like the niche to it.
OMG yes, somebody who gets it about Vault tying up too much of her optimal burst-damage! THANK YOU!! This' something I've argued a lot... having that extra mark tied to Vault is not cool. It'd almost be better to transfer the bonus mark to her Q, permitting multiple targets to be marked via good aim, & nerfing the bonus mark damage in exchange.