A quick update on the deck I've been enjoying on the MtGO Beta:

4 Lotus Cobra
4 Putrid Leech
4 Borderland Ranger
4 Ob Nixilis, the Fallen

2 Doom Blade
3 Sign in Blood
4 Harrow

3 Maelstrom Pulse
4 Grim Discovery

4 Garruk Wildspeaker

4 Verdant Catacombs
4 Terramorphic Expanse
8 Forest
8 Swamp

Sideboard
4 Duress
4 Malakir Bloodwitch
4 Gatekeeper of Malakir
3 Scute Mob

Yes, I have happily swung with an 21/21 Ob Nixilis after doming my opponent for 18.