I disagree with the banning of Deathrite Shaman for a lot of reasons. Although it is without a doubt one of the best one drops ever printed, it was not without it's drawbacks. It was actively bad against Tron and Affinity - you only had your own fetch lands, and life gain or loss was not very relevant in either match up. There is a fair argument that if Deathrite is left unchecked, it can win the game. But realistically, how many cards in Modern can win the game if left unchecked?
However, I do understand why Deathrite got banned. Modern has proven to be a format where a card does not have to be overpowered to be considered ban worthy. I believe Wizards banned Deathrite as a hit to both Jund and Pod, as opposed to hitting the two decks separately. Both decks do suffer without Deathrite, although Jund moreso. Without Deathrite, many cards and decks improve - Snapcaster Mage, Goryo's Vengeance, and Living End. Graveyard hate must be more direct, as opposed to the blanket protection provided by Deathrite.
Weakening Jund also de-polarizes the format. Previously, a deck had to go under Jund (Affinity), go over it (Tron), or out grind it (Pod). No other "good" deck could consistently beat Jund. Now, midrange has more possibilities.
I agree with Nacatl being unbanned. It was never overpowered to begin with - Green Sun's Zenith and Punishing Fire + Grove of the Burnwillows are what broke Zoo. I understand that Wizards banned Nacatl to promote alternate aggressive strategies, but that never came to fruition. Affinity has been the number one aggro deck since Nacatl was banned. I look forward to having Nacatl in the format.
I do not believe Bitterblossom is inherently an overpowered card. Making a 1/1 flier every turn is not that powerful compared to what a lot of other decks are doing. The 1/1s can also be answered pretty easy via commonly played cards such as Pyroclasm and Orzhov Pontiff. Bitterblossom is also puts very little pressure on combo decks. Bitterblossom also keeps Affinity in check, disabling profitable attacks from Signal Pest and Inkmoth / Blinkmoth Nexus.
My problem with Bitterblossom is Mistbind Clique. Faeries have seen some play as UR tempo, but have really been held back because they cannot maximize their Mistbind Cliques. Faeries now have a permanent that they can consistently champion. Abrupt Decay can answer Bitterblossom, however, Jund just got less enticing to play. Outside of Decay, there aren't any common forms of removal for enchantments. Mistbind Clique is an absolute beating, and I am not sure if it is healthy for Modern.
Although I do believe Faeries will be tier 1, I do not believe they will be as powerful as they were during Standard. Modern has many years' worth of tools available to handle any deck. Because of the way Modern has shaped up, I believe Faeries will be UB based, splashing red for Lightning Bolt, Electrolyze, and various sideboard options.
Overall, I think Jund will have to do some serious changing to stay as competitive as what it has been. It needs a new cheap value creature to replace Deathrite. Pod will remain unchanged - Deathrite was not a major loss. Graveyard decks such as Goryo's Vengeance, Living End, and Dredge got better. Midrange in general got better. Zoo is no longer a tier 2.5 deck, although it is yet to be seen if it is tier 1. BW tokens got significantly better. Faeries realistically exist and will be tier 1. Affinity got worse. The better that blue decks get, the worse that Tron and Splinter Twin get.