Thalia: I was sure that four was the right number earlier in the week but now I'm not as sure. You're right that drawing dead cards in this deck that doesn't have any card draw is a big problem. I may go back to three though I don't think I'd include a fourth in the board as I think there are other sideboard cards that are good against the same decks but have more utility in other matchups as well (maybe Canonist or something).
Crucible: I have one in the side now but it is definitely a maindeck-worthy card.
I like my board for shops now. With the list that I posted above I bring in
and I remove
I also take out Chalice on the draw.
I don't know if this is right or not, obviously. I am not sure about how to evaluate Containment Priest (and the Displacer combo) in any matchup other than the obvious (Dredge and Oath). But this sideboarding has felt pretty good.
I'm thinking of trying:
-1 Thalia, Guardian of Thraben
+1 Crucible of Worlds
+1 Reality Smasher
+1 Swords to Plowshares
And I'll replace the Crucible that was in the board with an Ethersworn Canonist, I think. Though I also wouldn't mind having a Ghost Quarter in the board as well (that could also get me a Plains in a pinch).