4 Alloy Myr is not a reliable enough source of red mana for the Bloodhall Ooze . I'd just take those cards out and add some mana ramp or more green/black creatures. Doomgape doesn't seem like a castable card with only Alloy Myr as ramp.

Maybe run a Sylvan Caryatid instead of the Alloy Myr and also Scavenging Ooze could be good in this also

+1, I really like this. I would say that unless regeneration is a real problem, you could take out Terror for a Doom Blade /Go for the Throat split.

Pssst... Urborg, Tomb of Yawgmoth

It's already in the maybe board. But I dont think its a good idea because of "in addition to its other types" where as Evil Presence and Contaminated Ground changes lands into swamps.. which makes opponents faces fun to watch. Especially when used on dual lands.

You can at least make it a 1-of since it doesn't take up a spot, and assurely secures your swampwalks.

Good, valid point, however, Urborg is too expensive for me.

Maybe as a 1 of, why not Erebos, God of the Dead ? Just saying due to the number of black symbols in your permanents to easily make him into a creature.