Quote from Tears of Tomorrow »I run Izoni IRL, and she's been giving me great results with a list similar to yours. Compared to you, I focus more on loading the grave quickly, by relying on abilities like Explore and Dredge. Life From the Loam is an exceptional card on this regard, as it keeps loading your grave with stuff and your hand with lands, which should solve the mana issue. Stitcher's Supplier has also proved to be exceptional for me. Losing combo pieces in the process hasn't been a problem thanks to cards like Seasons Past, Eternal Witness, and the new 4 mana Golgari creature that retrieves permanents froma grave.
A card I've been considering lately is Emrakul, the Promised End. I mean she's capable of having a huge impact on any game, and she likes a loaded grave and mana ramp, two things a Golgari deck should easily be able to provide.
I also value redundancy more than you: rather than running three combos, I run one combo, but with each piece having two or three potential replacements.