WorstBandNameEver, I tried your exact list at FNM last night and got second. I liked that there were multiple angles of attack beyond just making Marit Lage as fast as possible, but there were a few things I would recommend changing.
A
Bojuka Bog in either the MD or SB (cutting one of the Grafdigger's Cages?) would give you instant speed, tutorable graveyard hate with Crop Rotation.
Your list doesn't have a way to protect Marit Lage once she's in play. Since your deck is a little more controlling than the average Dark Depths build, I'd suggest
Steely Resolve, which protects Marit Lage from everything but Terminus and Liliana. You could probably cut one of the Pithing Needles and maybe the Toxic Deluge for two Steel Resolve.
Your deck also doesn't have a way to get Marit Lage past flying blockers like
Sejiri Steppe or
Shizo, Death's Storehouse. This didn't come up last night, but I could it see it being a potential problem. If you want to run one of them, you could cut the second swamp.
A little more speculatively,
Volrath's Stronghold could be used to recur dead Bob's and Hexmages.