I've been playtesting without Crop Sigil for a while now, and I haven't missed it! I don't really need the self-mill effect, and if I wanted / needed the recursion effect, I could just run Grim Discovery — 2 mana cheaper and no Delirium condition.

Crown of Vigor has a great sac effect in a tribal deck, but it doesn't really become useful until the Ishkanah engine comes online, and since the whole point of self-sac enchantments is to reach Delirium for Ishkanah, this card just doesn't fit the deck's needs.

Edge of Autumn was initially appealing because it was either ramp or a way to get both a land and sorcery into the graveyard via Cycling. However, we actually really want to reach 7 lands, not just 5, so sac-ing a land usually isn't appealing.

Lotus Petal seemed like an obvious artifact, but it doesn't replace itself (unlike cards like Mishra's Bauble). This deck tends to run out of cards-in-hand quickly if I don't have enough ways to replace those cards.

Memorial to Unity seemed like a good sac-land, but this deck doesn't run very many creatures, so there's too much a risk of this being "Pay 3 mana to put this land into your graveyard" with no other upside. The cards you look at don't even go into your graveyard, but bottom of library.

Primal Growth was carried over from Version 1 of this deck. I gave it a try, since ideally it would get both a sorcery and creature into the graveyard, and then it would be a very efficient "1 mana for 2 basics into play tapped" (effectively). However, the only creature that can really work with it is Renowned Weaver, but he was often needed as an early blocker. Tokens don't go to the graveyard, and by the time I'm creating tokens, I'm trying to stabilize, and losing a creature isn't a good idea.

In this deck, there's no reason to run Rampant Growth over Harrow, unless you're desperate for the Sorcery card type for Delirium. Otherwise, Harrow gets 2 card types into the graveyard and has a better effective rate (i.e. if you start the turn with 3 untapped lands, then after casting Harrow you'll end up with 2 untapped and 2 tapped, so it's effectively like you paid 1 to put a land into play tapped, whereas Rampant Growth costs you 2 to do this.)

Smallpox also seems great for Delirium (since it can potentially achieve it single-handedly), but more often it just felt like it was hurting me more than the opponent. I also had a harder time than I thought I would paying double black (despite full playsets of both Overgrown Tomb and Woodland Cemetery).

Subtle Strike and Wail of the Nim both have effects similar to that of Golgari Charm, and the Charm is just better overall. Plus, they're much less on-theme than the Charm.

Toxic Stench won't usually be good until turn 5-ish. In almost every case, Ghastly Demise will be the better option, as it can scale better in the early turns. It also costs 1 less mana — quite often relevant, as the early turns need to be very efficient. The ONE edge case in which Stench is better is when there's a 1-toughness creature you want to take care of on turn 2, and you don't have anything in your graveyard yet for Demise. However, it is very rare to have zero cards in your graveyard on turns 3 or later, so this is literally a turn-2-only edge case — not a good enough reason to run it instead.

After playtesting Unbridled Growth, I usually just ended up casting it in order to immediately sac it for a card. I never needed the mana fixing (I bet this would be more valuable in a 3+ color deck). So it's "{G}: Draw a card". I may as well just play Chromatic Sphere. Yes, you have to pay {2} initially, but you get a mana back, so effectively it's also "{1}: Draw a card" with one-time mana-fixing. More importantly, though, it puts an artifact into the graveyard. I don't need the "enchantment" type of Unbridled, since I have plenty of good enchantments vying for that spot.