The problem with this kind of card is that it's dependent on shuffling to not become useless once you find a card you don't want - and actively becomes worse if you use the evergreen mechanic scry.

Sure. We can also say that the problem with scry is that it's actively worse once you use the Nine-Armed Starfish mechanic. I don't think that means this mechanic, or scry, are bad, though.

It might mean that the mechanic would be better off in another color however. Maybe Green? Green likes to put cards from the graveyard on the bottom of the library. Would that be too easy a strategy to employ?

Lots of fun with Mistveil Plains

True.

I found this in a booster. I think it could be a black card since it's looking at "deep dark secrets". You could also add the option to put the bottom card in the graveyard which would also suit black. I have no idea why it's a starfish.

­Sigiled Starfish.