Tireless Tracker basically has landfall, even though it isn't technically printed on the card. It's great if the game gets grindy, providing plenty of card draw, but weirdly I'm never excited to see it, so I've dropped it for now.
Courser of Kruphix really seems like it was made for this deck, but my experience so far has been that getting lands off the top of the library and the life gain aren't that critical. Plus, having Tireless Tracker and Scute Swarm as 3 drops means the Courser is kind of clunky. For now I'm happy with the Jaddi Offshootss in the sideboard for burn matchups, but I'm not counting the Coursers out entirely.
Blighted Woodland... Does it look good and is it on theme? Yes. Is it really necessary? Probably not. Usually getting extra landfall triggers is less of an issue than getting the crabs to stick around long enough to make the landfall matter.
Druid Class was recommended for damage mitigation. I have Jaddi Offshoot in the sideboard for damage matters matchups, but I do likt that Druid Class is somewhat harder to remove as an enchantment and the level 2 could be useful.
Khalni Heart Expedition used to be in the main but I dropped it for Harrow. They both get two land drops and harrow has the upside of being an instant and not needing any additional setup. It also has the down side of sacrificing a land (which hurts if it gets countered) and costing more. I'm still not sure which I prefer.
World Shaper was suggested to me as a deterrent to creatrure-based strategies and a potential for a flood of landfall when it dies. Without a way to reliably kill it myself, I think it would mainly be a sideboard card, but I really like the concept. Testing is in progress.
Counterspell and other control cards are something I've tried to avoid because I'm not a fan of control and I feel like I always use it as a crutch when I'm in . However, the lack of interaction in this deck can leave it vulnerable and the right balance of crabs to counters would likely make it much more resilient.
