I just wished to share some thoughts on these Vayne changes. Personally, I still like her the way she is on live, but I am open to changes. The Q and W changes make sense to me and seem fine, but I just feel like the ult change doesn't fit Vayne's kit.
W in particular specifically rewards attacking the same champion, and these ult changes don't contribute to that duelist identity. In some situations it may even encourage you to keep 'tagging' everyone, instead of focussing on one target like the rest of her kit encourages.
If the goal is to increase her survivability, a possibility that would still fit her identity as a duelist/1v1er could be something like tying a heal (or alternatively something like a damage reduction like Phantom Dancer's) to proccing her W during her ultimate. Something that would contribute to her 1v1 identity. Just a suggestion.