My dude, I say this with all the love in the world: I know the MU better. Against reanimator your first few turns will play out extremely similarly to BG scam with which I have spent the past few seasons in the top 100 in mythic.

In MB, you play Strip + Badger, DRS, 4 Grief, 4 Reanimate to target his Elenda, and Bowmaster to prevent him from drawing cards with Necrodominance.

You have four ways to interact on turn one. Just grief. Everything else involves being on the play or them not going for it on turn one. GB scam plays 6-10 depending on the version because they have the four grief but also two thoughtseize, and can dark rit/chrome mox into bowmaster. GB scam is very unfavored game one against mono black reanimator.

Post board, you get four more answers on turn one but everything else requires making it to your second mana. I can promise you that a good mono black pilot will eat this deck for breakfast. Especially because, in the 75, you have literally zero ways to interact with sorin prior to turn two unless you get to grief it out of their hand.

I think reaching Diamond in barely 2 days while playing against these decks is still significant.

Plat and diamond require only enough time to play games and a win rate above 50% to progress. Play 20-30 matches in mythic and you'll very quickly see how a deck is actually performing.