There are some big changes coming to Standard (and Wild to a lesser extent) with the recent balance changes. Most of the top tier meta decks are taking a hit from these changes, with perhaps Warlock taking the biggest of all.
First off, Dark Pact and Possessed Lackey are being nerfed. Dark Pact will now heal only 4 Health instead of 8. This is a pretty significant change and will certainly require players to consider their life total a bit more in certain matchups. Previously, a double Dark Pact turn could reverse almost all the work an aggressive deck had put in so far. Possessed Lackey is moving from costing 5 to 6, which is an interesting change. I am not sure how this will affect play. I suppose the question is whether paying 6 for a Doomguard in Cubelock is worth it. Control Warlock most certainly continues to play the card for big daddy Voidlord, however, as that's still quite the deal.
Next is the deck that just can't stop getting nerfed: Quest Rogue. At this point, Crystal Core has to be a massive design regret for the development team, right? What are the odds this card gets nerfed again? There are so many cards that make the deck consistent and capable of closing quickly that I'm legitimately curious if it continues to be a problem. While the change to 4/4s slows the clock down significantly for the deck, I imagine the deck continues to see play as a way to punish control decks that fail to close games quickly.
Speaking of closing games quickly, both Murloc Paladin and Even Paladin are taking a fairly large hit, as the cost of Call to Arms is moving from 4 mana to 5. I actually think is a fairly healthy change, as games where the card comes down on 3 and 4 with a coin feel incredibly unfair and miserable. The card is just so consistently powerful, and cheating that many 2 mana minions into play with a follow up Sunkeeper Tarim is quite the play pattern.
Spiteful Druid is also taking a nerf, as its namesake card, Spiteful Summoner, will now cost 7 instead of 6. As Spiteful Druid is a "curve" deck, in that it wants to hit powerspikes along its mana curve, this is a fairly relevant nerf to the deck. However, I think the deck probably sticks around for a while and Summoner is powerful enough that it remains in the meta.
As for the wild meta, Naga Sea Witch is taking a hit. This change is meant to slow down the pace of the Wild Giants decks that dump a host of 8/8s on to the board before the opponent can do much. The deck is considered a dark spot on the Wild meta, as like the Barnes decks of the previous standard, games are often lost without much interaction. Blizzard had said that the deck's winrate was not problematic but this change is more for play pattern than anything else.
Some decks in the Standard meta probably stand to benefit from these changes that haven't taken a hit on these changes. Namely, I'm curious if various Priest decks can move their way to the top of their list. I think aggressive Rogue strategies might see an uptick in play, as well. In any case, these are fairly healthy balance changes that help make room for some of the other classes. Maybe Shaman might even become playable again!