I can take a closer look at each one, but here are a few quick suggestions.
For the Dimir deck, if you're looking to mill them out you'll need a few pieces. First, you need some way to exile the two legendary Eldrazi (Kozilek and Ulamog) otherwise you simply cannot win via milling. Those two will simply cycle into their yard, return their yard to their library and BAM you're out of luck. This sort of stuff can be achieved with Cremate or other items of a similar nature. Cemetery Reaper also comes to mind. As an artifact to toss in, Keening Stone is HUGE as you can realistically mill someone out (even with 100 cards) in 3-4 hits with the stone, especially if you've been milling a bit here or there already.
For the Golgari deck, a few pieces I would suggest include: Skullbriar, the Walking Grave strikes me as an interesting general. It gets bigger and maintains those counters unless it's returned to your hand or your deck. Presumably this means it would also maintain those counters in the command zone - making it quite the threat for general damage quickly. Tack on scavenge creatures (or just Varolz, the Scar-Striped in general) and you can imagine the potential. Toss in Rogue's Passage/Whispersilk Cloak to make him unblockable and the opponent already has a quick clock (not a common occurrence in EDH in my, admittedly limited, experience. Vulturous Zombie is another card to be sure to include as it can be HUGE without much effort. Something hitting the yard is a low bar, making them casting spells and discarding both resulting in it being pumped.
I can mull them over a bit more, but those were my first impressions.