I've seriously considered replacing them with either more removal or Skull Prophet (and maybe even Excavation Mole). In others they are just overcosted self-mill. Ashiok, Dream Render and Tamiyo, Collector of Tales are the two highest variance cards in the deck.They are also the reason no Narcomoeba (a free 1/1 flyer just isn't worth the slot against most decks).

The lack of Prized Amalgam and another turn one mill play like Stitcher's Supplier is a big reason why. The deck is grindy, not explosive like other dredge decks.The bad mana base is also why only three Merfolk Secretkeeper // Venture Deeper as with only five untapped blue sources it is unlikely to get the dream draw of turn 1 Venture Deeper into Creeping Chill & Silversmote Ghoul (I did get it once though, it was nice).Fabled Passage is the all-star land of the deck since it can be looped with Glowspore Shaman and goes to the graveyard when cracked. But despite that I don't think the deck can afford to play more non-basics. This is what I am currently planning on testing some more.

I spent most of last night playing through a ton of different versions of this deck on Arena.

Mtg standard dredge