So, for Pox Sideboards, I think having less than two pithing needle is just wrong, as you will always have something relevant to name in a surprisingly large number of matches (Jace the Mind Sculptor, Rishadan Port, Aether Vial, Thespian Stage, Knight of the Reliquary, Kuldotha Forgemaster, Karn Liberated, Sensei's Divining Top, Scalding Tarn to name a few...) and I think you should have at least four relevant GY hate cards (Grafdigger's Cage, Leyline of the Void, Extirpate, Nihil spellbomb, surgical extraction. those are the 5 that i usually rotate between depending on what i expect.) I also usually aim for 3-5 board wipes or removal spells depending on how i feel the meta will line up. one is usually Night of Soul's Betrayal, Dread of Night or Engineered plague, the others are usually between BSZ and Toxic Deluge, with spinning darkness, murderous cut, and collective brutality for the point and click spots (collective brutality is phenomenal by the way. just putting that out there.) The rest of the SB slots can be tuning those numbers, adding more tax effects ( I like a second nether void in the 75 somewhere, but trinisphere and sphere of resistance do similar things) against the combo decks, additional discard rarely hurts (hey, collective brutality...) or golden bullets for whatever matchup you just don't want to lose to (deathgrasp and gloom vs enchantress, pox vs miracles, sun droplet vs burn, to name a few.)
I think that Liliana the Last Hope is a card that i'm going to keep two copies of around because she seems absolutely bananas if the meta shifts towards D&T, which it looks like wizards is pushing a fair bit. She also seems very good at playing a second copy of The Abyss vs. Elves and Goblins if the meta slants that direction. I don't see her being more than two in the 75, and it would take a very special set of circumstances for her to be a main board slot, but most of that comes from sharing a planes walker subtype with ms. veil, who helps make our deck click together and hum as efficiently as it does. That said, I can see a meta (or a budget constraint) where a 3-1 split in the main with another of either (or both) in the board is worth talking about, partially because she does, as mentioned, just end the game in a hurry (especially in the miracles and Shardless matches). I would be less shy about it if her -2 was relevant to non-tombstalker or loam versions of the deck.

