Pyxis can also just be another card that helps you win, by decking them.
Statistically, the utility of having more mill rocks is outweighed by the benefit of the card that you are getting rid of.
The deck is not supposed to be fast. you're not trying to increase the number of cards you mill. You can win an entire game with lantern and 2 mill rocks (i've done it). The deck isn't about the mill. It's about the lock. Once the lock is in place, 99% of the time they will not win the game.
*social commentary time* I've played this deck for years, and I have I think two different versions saved on the site
https://deckstats.net/decks/42006/369912-lantern-cuntroll/en - First one
https://deckstats.net/decks/42006/905603-they-asked-me-not-to-play-this/en -
Second one.
This is actually the problem with a lot of people who try to play lantern. You can't look at it as a mill deck. It's a prison deck. I've played games where I couldn't mill more than one or two cards per turn because of their board state. So even though I had all 7 of my mill rocks out (yes, I only run 7 total), I had to
hide behind the lock.