The Game Director took to Blizzard's forums and shared Team 5's take on the card rotation.
With the announcement of Standard in Hearthstone Blizzard implemented a way to keep the game's meta fresh, to prevent an overly full card base and to ensure new players would still be able to jump into Hearthtsone. However, only expansions and adventures would rotate, whilst the Classic set would remain. This immediately raised the eyebrows of many people, as some Classic cards have been present in viable decks since the launch of Hearthstone. [card]Azure Drake[/card], [card]Ragnaros the Firelord[/card] and [card]Sylvanas Windrunner[/card] are cards often discussed for this reason.
On the Hearthstone forums the topic of Standard and the Classic set was raised once more, and Ben Brode gave more insight.
Brode: The goal with Standard is to keep the meta fresh for each yearly rotation. There are some benefits to keeping Basic and Classic cards in Standard: Returning players have an entry-point to the new format, and new players experience classics like "Hogger" and "Arcane Missiles" that are iconic and great introductions to the game. People take breaks from Hearthstone, and being able to jump right back in with a few cards you already own and understand makes that experience a lot better.
That upside has a real downside in working directly against the big goal for Standard. It needs to feel different each year, and if Basic and Classic cards are still appearing in large densities year after year, we will not be achieving our goals for Standard.
We knew we weren't going to get there when the Year of the Kraken began, so we nerfed 12 basic/classic cards, to put more of the weight of the meta into the rotating sets. We always knew we'd have to watch the meta to see if any future changes would be needed when we got ready for the next year of Standard. If things are looking like they are going to be too same-y for that next year, we could see more nerfs, or we might rotate some additional classic cards to Wild, like we did with Old Murk Eye. No matter what, we're committed to making Standard fresh and exciting each new year.
Following up on the topic, another question was asked on the forum:
Are you guys considering, besides nerfs, implementing buffs for underused vanilla cards?
Brode: Given the goal of Standard is to keep the game fresh each year, it's important to keep a lot of the power of the cards in the expansions, and not in the basic and classic sets. It's not clear what that balance of power should look like (is it ~10 cards from the basic and classic sets on average?), but we're currently skewed so high towards basic and classic cards in decks, that we are at high risk for 'samey-ness' as the years change in Standard. Buffing Basic/Classic cards *increases* that risk. If the goal is to get more cool cards into the meta, just releasing awesome new cards in expansions should make an impact there, and still keep Standard fresh.