Lavinia is just another hate card that you must answer in order to go off. Stony Silence has a similar effect on the deck and was already pretty much ubiquitous. All you have to do is diversify your answers /Threats.
Aren't Karakas and STP better than what red brings to the table though? Also, Mentor is really good in the matchups where Outcome isn't as good and white is better at helping you fight Stony Silence.
I personally wouldn't want to play the deck without Key Vault and LoA.
Key naturally synergizes with the deck and key vault is far more resilient than tendrils (especially when Lavinia slots replace Stony slots).
Library can make or break a game and even if it's only relevant 10-15% of the time, still worth the inclusion over another random land.
If you think Xerox is "really annoying right now", you probably weren't playing when Mentor, Gush, Probe and Dig Through Time were unrestricted. The current versions of Xerox have way less inevitability due to having worse win conditions and being far less consistent at outdrawing other decks (which limits their ability to maintain a counter wall and to find their silver bullets).
Shop lists rarely have more than 1-2 Metamorphs in a deck that lives of the top of its deck. You also have more Hurkyl's recalls than they have metamorphs to help make your Blightsteel effective in the matchup.
Tinker has never been a great answer to dredge and isn't in the deck for that matchup. It's meant as a backup plan when facing hate.
Inkwell is better vs blue decks, but again that's not the matchup where you want Tinker. It's a lot worse than BSC in the matchups where you tend to rely on tinker.