Great questions Derek. Cutting Black Sun's Zenith was a very intentional decision. I do not like the card at all right now because it does not do as much as it used to. There are too many recurrable threats, counters, and high toughness creatures for it to be effective. Using it against Dungrove Green is not a winning battle for you either. I did add the Blasphemous Acts to the sideboard for that specific reason though.

The mana is rarely an issue for me for a couple reasons. Number one is the manabase. I spent a considerable amount of time tweaking it so it was as good as its going to get. You always have sphere of the suns to help you out as well as rampant growth and solemn simulicrum. So even if you dont have a forest in play, you still may be able to cast primeval titan on turn four. The green suns zenith does help fix the mana as well because i can get birds of paradise or borderland ranger. The borderland ranger has been good enough that I even considered adding more of them in the deck.

I am undefeated against Delver in competitive play with this deck. The reason the delver match is so good is because you can kill all their other flying threats with a variety of cards in your deck. I did play two phyrexian metamorphs specifically for killing geist though. I know it seems like geist would wreck this deck, but it doesnt play out like that.

Dungrove is a different story all together but that match is winnable, just not great. I did not lose to any aggressive decks either and I would have liked to play against more of them because of how good those matches are.

The one of huntmaster was awesome for me. you can cast it pretty easily by fetching a mountain, casting sphere, or just naming human for your cavern of souls. All of those are viable options. Cavern allows you to do a lot to fix your mana, you just have to put a lot of thought into what you want to name with it. I have named every creature type with it. The ability to name Human, Spider, Elf, Golem, Shapeshifter, Giant, and even bird is all been part of the reason that Cavern is so good.

I'm curious, though – your mana seems dangerous. When I played the deck, my biggest issue was the unreliability of the mana – having double black on the necessary turn to cast something like Geth's Verdict was hardly a guarantee. I got smashed by Geist of St. Traft a frustrating amount of the time. Have you found the number of creatures you have in the deck sufficient to stop early aggression from tough to deal with creatures like Geist of St. Traft and Dungrove Elder? Huntmaster is nice, but makes the mana even more difficult.