Hearthstone's latest patch changes just one card in the game. However, this tweak completely disrupts a very powerful deck in the multiplayer card game.
Warsong Commander, a basic card for Warriors, previously gave Charge to any minion with less than 3 health summoned by the player. However, with today's patch, Warsong Commander no longer grants Charge. Instead, it gives +1 Attack to any minion that already has Charge.
The problem wasn't with Warsong Commander itself. Rather, Blizzard had made this change to weaken a popular combo many Warriors were using in recent months. They would create decks with Warsong Commander as well as Grim Patron, a card introduced with the Blackrock Mountain expansion. Grim Patron is a low-cost minion that summons another Grim Patron whenever he's damaged. Again, not a crazy powerful card but very deadly in the right combination.
A Warrior with the Grim Patron deck would get Warsong Commander onto the board and then a Grim Patron. Then they would find a way to damage the Patron so it would summon a copy of itself. Warriors have a lot of cards at their disposal that can do this. For example, they can use Whirlwind to hit all enemy and friendly minions for one damage. Inner Rage, a card that costs zero mana, hits minions for 1 damage and then boosts their Attack by 2. The player could also make their Patron attack an enemy minion. Whatever the method, the result was the same: a new Grim Patron would be summoned and, thanks to Warsong Commander giving it Charge, it could attack right away.
If the player had enough mana, they could keep damaging their Grim Patrons and summoning more. Given the right combination, you could end up with a small army of Patrons that could attack before the enemy was even able to respond.
Grim Patron and Warsong Commander were even more powerful when combined with other Warrior cards that benefited from a minion taking damage. Frothing Berserker gains damage every time that a friendly minion is hurt. Battle Rage gives the player an extra card for every damaged minion on the board. Armorsmith provides the player's Hero with extra armor each time an ally is hit. It's easy to see how matches could snowball out of control.
Blizzard's decision to nerf Warsong Commander shows how serious of a problem they thought this combination is. The development team is generally averse to changing cards after they've been released. They've only stepped in a few times to nerf overpowered cards. Community manager Zeriyah reiterated last week that they prefer to add new cards that can counter the old ones:
Going forward, we will continue to stand by our stance that we will only make adjustments to cards when we feel it is completely necessary and allow the injection of new cards into the game help our players define what the meta evolves into. In the case of Warsong Commander, we felt this change was necessary to help expand both future design space and to stand by our overarching game philosophy that battles between minions and fighting for board control is what makes Hearthstone fun and compelling.
Designer Ben Brode explained in a follow-up video that the Warsong Commander/Grim Patron strategy "feels really bad to lose to" because because you can't react to a mass of Charging minions. Furthermore, the Grim Patron deck punishes you for playing minions, because these minions become an easy way for Grim Patrons to get damaged and spawn duplicates of themselves. They decided to weaken Warsong Commander rather than Grim Patron because the former grants the Charge, which they consider one of the least fun mechanics in the game along with direct damage. Furthermore, they felt that Warsong Commander's ability to grant Charge to allies would continue to be a problem in the future if not removed.
Brode conceded that Warriors are currently one of the worst classes in Arena mode and this nerf could make them dip further. He says that future expansions could bring new cards or features that will strengthen the class, though.