Set rotations have always been a time when the game is most exciting to play. The addition of new cards coupled with stale ones leaving for Wild make for an extremely compelling and fresh experience. Whispers of the Old Gods and Journey to Un'Goro have consistently placed high amongst players' favorite expansions.

Expectations were high for The Witchwood despite the concerns that most of the core cards in the most powerful decks of Kobolds and Katacombs were not rotating out. The reason for this expectation had a lot to do with what happened a year ago. Journey to Un'Goro was billed as having the highest number of unique mechanics in a single expansion ever. Because of that, subsequent expansions have had to be powerful to be relevant at all.

Now that The Witchwood is in the hands of millions of players, many have expressed concern about the set's level of impact. Anecdotally, the decks and archetypes that dominate the ladder appear similar to those that the community experienced during the last expansion. The aim of this article is to quantify the impact by looking at the play rate of cards by set and to establish where The Witchwood ranks in comparison to the other expansions.

New and Fresh

The simplest measurement of the impact of a set is the play rate of the cards within it. However, it should be noted that Genn Greymane and Baku the Mooneater complicate this a bit since their impact has little to do with their play rate.

Figure 1: Share of play rate by set. Major milestones are indicated. Toki, Time-Tinker summons omitted. Core = Basic, Expert1 = Classic, OG = Wrath of the Old Gods, Kara = One Night in Karazhan, Gangs = Mean Streets of Gadgetzan, Ungoro = Journey to Ungoro, Lootapalooza = Kobolds and Katacombs, Gilneas = The Witchwood.

What's immediately apparent is that when compared to Journey to Un'Goro during its launch window, The Witchwood cards have seen far lower play rates. Journey to Un'Goro cards saw play rates over 25% in its first week, whereas The Witchwood is closer to 10%. This is despite the significant decrease in the play rate of Classic and Basic cards over the Year of the Mammoth. Currently, The Witchwood is arguably the least relevant set, and even more concerning is the continuing decline.

With the current design of set rotations, Blizzard is stuck between a rock and a hard place. They either have to:

Constantly increase the power level so that the most recent set is the most relevant; or

Reset the power level each year, avoiding power creep but sacrificing the relevance of early sets.

Blizzard appears to have chosen the latter for The Witchwood with a moderate power level. This is an amicable decision, but clearly at odds with their stated goals for standard to keep the game fresh particularly at the beginning of the new year. With this in mind, it seems reasonable to expect nerfs in the near future. Changes to cards like Carnivourous Cube, Spiteful Summoner and Call to Arms (and Naga Sea Witch while we are at it) would go a long way to freshening up the current meta (and future ones).

A Bigger Issue?

While new cards are an important part of keeping the game fresh, so are the old ones. The data suggests that even as Blizzard has been nerfing and removing key cards from the evergreen sets, their play rate collectively still sits above 45%.

What this means is that you're still hoping your opponent doesn't have a Mana Wyrm on turn 1, playing around Brawl, and getting wiped out by "Equality-Consecration" with no end in sight. While the pros and cons of having evergreen sets are well discussed, it's another discussion as to the magnitude of the influence these sets should have. Is there a middle ground where we still have an evergreen set, but the cards are not played as much? Is it reasonable that more than 40% of Hearthstone play should not change ever? Would it be easier to engineer change if their power levels were lower?

With The Witchwood, Blizzard appears to be attempting to rein in the power level. This is an admirable goal since if left unchecked, sets will continue to become more and more powerful to the point it's detrimental to the game. But with such powerful cards already available, deck archetypes like Cubelock and Aggro Paladin might stick around all year long. Based off of the above data, it would be hard to imagine Blizzard not considering some nerfs in the near future.

Bonus

The following shows the same data but for wild (thanks for the feedback). It gives some indications of the power level of all the sets relative to each other.

Figure 2: Share of play rate by set. Major milestones are indicated. TEMP1 = The Grand Tournament, FP2 = Black Rock Mountain, HERO_SKINS = Hero Powers, the rest should be self-explanatory.