Sanctuary traditionally these decks have been split between two types: control mill and turbomill.
Most of the early turbomill decklists I saw were in simic colors or izzet, relying on a few fog effects or burn spells to slow down an opponent. The core of these decks is the draw engine, drawing a lot of cards not only helps you win faster, it allows you to run relatively few answer cards against your opponent. Geg's build is a turbo approach because it devotes a lot of cards to the draw engine and few cards will permanently answer a threat. However it is much more resilient than a typical turbo list, there aren't many answers but they are very flexible. You can hold out a long time.
I gravitate towards more of a control approach. Start with 2 tutelage instead of 3, and then instead of filling the deck with cantrips focus more on answers that can deal with whatever your opponent throws at you. You presented a lot of "what if" scenarios, a control mill decklist should contain answers to anything in the meta. But these decks take much longer to win and are more vulnerable to draw randomness. A control mill deck might take 40 turns to win vs 20 for turbomill. I posted my decklist in the Jeskai thread and some people have had success with it, although I don't consider it a finished list due to my limited testing.
I don't think there is necessarily one best approach, it depends on the meta, and metas are different on each platform. Just keep in mind that while you can build a deck that tries to answer everything, it will end up creating other problems.
Ironically, the Chandra scenario popped up with Nissa instead during the next game. Fortunately, I had a Fleshbag in hand. Fleshbag also stalls the game after a Languish, and synergizes with the Skaab. Like I said, it needs permanent solutions, otherwise you're just basically spraying and praying that you get the cards you need to finish them off. Look at the above screenshots.
Also, one of the games that I lost when playing the build exactly as it is here, was to a 6/6 flier that I had absolutely no answer to after a Languish. Even if I had a Fog, that's just one fog, and there was only a single Tutelage in play. Good game? Plus, mixing around Skaab, Fleshbag, Dispersion Wave and a few draw cards isn't having too many cooks in the kitchen. It might win 1-2 turns slower than the version with three more draw cards, but it will be more consistent. Although I'm not sure what the right mix would be yet. I keep ending up with Skaabs being held with nothing really to use them on. Should I just be dropping them to get more draw cards out of the grave, instead of holding off for another Fog or possibly Languish? More often than not I am holding Dispersion Wave for the majority of the duel, and then when I am about to use it, I draw the second. Which never gets used.
While this isn't indicative of the functionality of the deck, duels like this are always fun too:
http://images.akamai.steamusercontent.c ... 71090056B/Anyway, I'd like to know what your win rates are with a Mill deck, regardless of what kind it is. Both of the R/G variants seem to blow it up easily. Or at least, I've never been able to beat one, and I've also never been beaten by a Mill deck when playing either of them myself.