Power creep

Power creep, otherwise known as powercreep is a process that sometimes occurs in games where new content (in this case cards) slowly outstrip the power of previous alternatives. This leads to players abandoning previous options in favour of the latest and more powerful alternatives, resulting in an inevitable increase in power throughout the game

Power creep in Hearthstone was a common topic of discussion from the game's launch, with many players regarding it as a negative, if a somewhat inevitable problem, due to the need to keep adding new cards, which would have to be relevant and desirable alternatives to those already available to players to be worth considering. Because of the ever-growing pool of cards and the potent cards already in play, the introduction of new cards was considered to almost inevitably lead to power creep, in order to prevent new content releases from becoming irrelevant, and the meta from ossifying. This was considered negative both in the devaluing and abandonment of older cards, and also in the increasing ridiculousness of the power level of new cards, as well as balance issues regarding other elements such as Hero Powers and hero Health pools. The matter was widely discussed, with the developers for a long time stating that the problem was "something we're spending a lot of time back at Blizzard thinking about" and had some ideas on how to tackle, but that they were not yet ready to share those ideas.

In February 2016 Standard format was announced, providing a solution to the game's ever-growing card pool, as well as a means of avoiding power creep. Due to the regular removal of cards from older sets, the overall size of the valid card pool would be capped, and the loss of key cards would alter the meta significantly, opening up new avenues for the designers to innovate along, allowing for new cards to reinvent the game rather than needing to constantly up the ante.

Ben Brode
Prior to the announcement of Standard format, Ben Brode had addressed the topic of power creep extensively, including in two videos on the subject. Overall, he conceded that some power creep was inevitable, describing the topic as a catch-22 situation.

In response to wide-spread claims of power creep, Brode states that making cards that are strictly better than other cards does not necessarily represent power creep, for several reasons. For example, Ice Rager is a strictly superior version of Magma Rager. However, Magma Rager is in the Basic set, and thus available to all players, while Ice Rager belongs to the Grand Tournament set, and thus requires collection through cards packs or other rewards. As such, Brode explains, this does not constitute power creep, but rather a path of progression for players to obtain upgraded versions of the cards initially available to them.

Dr. Boom vs War Golem is another example, with the former card being far superior to the latter. However, the former is an extremely costly/difficult card to obtain, while the latter is available to all players in the Basic set; as such it represents a path of progression rather than simple power creep.

Brode states, "you can tell if power creep is occurring, if the decks that people are playing... get more powerful. ...the output of power creep is that people are playing more powerful decks." He further explains that if the developers make a card which is more powerful than other options, but which does not get played in the meta, and thus does not increase the power output seen in-game, it does not constitute power creep. In another video, Brode states that power creep can also occur through new cards increasing the power level of other previously existing cards, leading to a sudden rise in power output in the meta.

This also addresses the topic of power creep over cards which are not commonly played, with Brode stating "if I print a card, then realize it is so bad that nobody plays it, I should be able to print a better one." Because the card is not being played, creating a superior version does not constitute power creep since it does increase the power of cards seen in regular play.

However, Brode has stated that some power creep is inevitable, stating that in order to keep the game fresh the developers have to make powerful new cards since if new content is not sufficiently powerful, players will not bother to include new cards in their decks. On the other hand, if each set of new cards is too powerful, the game will rapidly increase in power until it is almost unrecognisable, and older cards are never played. The developers recognise that this is a problem and one that will need to be addressed in order to ensure the long term health of the game.

For a broader definition of power creep and an incomplete list of power creeped cards, see List of Powercreeped Cards

Extra Credit
Extra Credit has a series regarding power creep using Hearthstone as an example of how to avoid it and the challenges involved. The series presented the concepts of Power Curve and The Delta of Randomness.

"The power curve of a card game referees to the curve created by plotting the power and cost of each card on a graph. While there will be some variation all of the game's cards should basically fall along that curve. If a card spikes too high over that curve it risks breaking your game. If it spikes too low it risks being too weak to be worth any player's time."

Magma Rager and Booty Bay Bodyguard were so far below the power curve when The Grand Tournament came out that they didn't see play in constructed and their replacements, Ice Rager and Evil Heckler, were still below the overall power curve so these two particular cards were not examples of power creep.

The Delta of Randomness is a card's minimum and maximum distance from the power curve. The larger this Delta the more "swingy" a card is. For example, in over a 1000 games the card may come out as a 50% win-loss "but players don't play in incriminates of 1000 games, they play one game at a time". The problem with a very "swingy" card is that when it works it "leaves the other player feeling the game was unfair”. This perception of unfairness, not power creep, was the likely reason behind the nerfing of The Caverns Below.

The biggest challenge with Power Creep is unforeseen combinations. This future-proofing explains the nerfing of Dreadsteed; when combined with Defile the card shot too far above the power curve.