The Old Decks
Now that we have an understanding of the new cards, we need an understanding of what this set and the new threats it brings will do to the decks that currently exist in the metagame.
MegaZone
This deck performed best at Regionals, winning two and placing second at two. It suffers from two things, however. Firstly, it has a virtually unwinnable Durant matchup. It also suffers from Eviolite, which makes Yanmega much harder to use against the dragons - especially Zekrom. It also doesn't gain much from the set; it can't make great use of N, Rocky Helmet, Eviolite, or any of the cards in the set.
Expected Change:
Tier 1 >> Tier 1.5 Zekrom
This deck stole one Regionals, and got two second places. Eviolite makes it much stronger. It doesn't particularly struggle against Durant or Kyurem, and because of how quickly it sets up, can hold its own against "Victini lock." Really, not a lot changes here.
Expected Change:
Tier 1 >> Tier 1 Stage 1 (Donphan/Yanmega)
This deck surprised everybody by winning a Regionals, and taking second at one. However, it gets severely hurt by the release of Eviolite, and hates playing Durant. It didn't even have exceptionally good matchups in the old format, and why it placed well is a mystery to me. It wasn't ever really Tier 1, even back in the Nationals/Worlds format.
As a side note, Donphan/Dragons should also be hurt. Tornadus now destroys Donphan, and Donphan can't even OHKO a Zekrom after it uses Bolt Strike without a PlusPower. The deck underwhelmed at Regionals, despite its good MegaZone matchup.
Expected Change:
Tier 1.5 >> Tier 2 Ross.dec
Ross.dec is a metagame counter deck. It plays to beat a set group of decks. With the release of a new set, what the set group of decks is is thrown into question. The deck has been struggling against Durant, and even Kyurem is capable of threatening it a little, since it can Outrage KO both Donphan and SEL. It almost forces the deck to include a metal attacker, for the purpose of beating it. Cobalion is the obvious choice, since it has enough HP to take hits from most things.
The deck, contrary to popular belief, is clearly still viable. It won one Regionals and placed in top 4 in two mroe. However, it's a hard deck to play when there's no defined metagame. Until we know what the metagame is, it's probably not the best play. However, if Magnezone gets weaker as I predict it will, this deck could become much stronger in turn. It might need to make some changes to apply for Durant and Kyurem, however.
Expected Change:
Tier 1 >> Tier 2 (temporarily) >> Tier 1-1.5 Magnezone/Emboar
This deck underperformed at Regionals. It got one second place, but that's it. However, it was horribly under-represented when compared to everything else. It can beat Durant through the use of Emboar's attack, and it can beat Kyurem through sheer power. It also played very well against the majority of the format before NV was released. The deck is not hurt by N at all. It is one of my top choices for Cities right now. This might change after the format develops more.
Expected Change:
Tier 1-1.5 >>> Tier 1-1.5 Gothitelle
This deck got a lot of hype going into Regionals, and was well represented, yet its best finish was one top eight. Rossbox completely outdid the deck. However, I think this came down to one simple fact: Gothitelle was the deck to beat for Regionals. Nobody wanted to go into the tournament with a bad Gothitelle matchup, which is proven by the "techs" used in the winning TyRam decks. If the format shifts away from Gothitelle again, it has the potential to come back and be one of the top decks. It doesn't particularly struggle against Kyurem, but Cobalion is stupidly annoying to play against, and it's not great against Durant. Rocky Helmet is also very hard for it to play around, especially in 30+3.
Now is a good time to mention one card that could find its way into the deck -
Leavanny. Pre-NV, the only hard counter to Gothitelle was Mew. By adding a 1-0-1 Leavanny line, Gothitelle can, for lack of a better way to say it, counter its only hard counter. I do not think this will be enough for it to make a comeback, however, since Mew wasn't a great deck to begin with, despite its overall strength against Durant.
Expected Change:
Tier 1-1.5 >> Tier 1.5 Reshiram/Typhlosion
Finally, Reshiphlosion. This deck managed to win two Regionals. However, neither of the decks were pure Reshiphlosion. One used Kingdra, and the other was won by an old friend of mine with Magnezone. It was clearly a strong contender in the last format.
The deck hasn't showed any signs of struggling against Durant or standard builds of Kyurem, and if you setup, Sharpedo's hand disruption won't do anything to you, since everything you need to keep attacking is on the field. Similarly, the deck doesn't particularly mind getting hit with an N, so long as you have enough Reshiram on the field before it happens. N does, however, make Ninetales a necessity again.
It gets some pretty extreme benefits from both Rocky Helmet and Eviolite, too; especially Rocky Helmet. That card gives the deck a fighting chance against Gothitelle, although I think running one Magby is still necessary, too. Rocky Helmet won't win the game against a smart Gothitelle player; it will just make it take longer for them to win. Hopefully more than 30 minutes and three turns.
I do not like Reshiram as a deck. It has a very one-dimensional game plan, and is very predictable. It tries to be as fast as it can, but at the same time as powerful as it can, and it ultimately ends up not fully having either. Still, once it is fully setup, its consistency is unmatched by any deck in the format, and 130+ HP basics dealing 120+ damage should not be under estimated. The consistency of the deck makes it the best play going into an untested format, especially since it hasn't struggled against any of the hyped new decks/cards.
Expected Change:
Tier 1 >> Temporary BDIF >> Tier 1