It's an eventful time for Hearthstone, Blizzard's wildly popular digital card game, with the Year of the Mammoth coming to a close and The Witchwood expansion promising to kick the Year of the Raven off in a big way.

To get some perspective on the state of the game I spoke to two members of the Hearthstone team, Dave Kosak (Lead Mission Designer) and Dean Ayala (Game Designer), at the 2018 Game Developers Conference. The two shared their insight into the upcoming Witchwood expansion, the end of the Year of the Mammoth, and the factors that motivate the team to nerf troublesome cards.

GameCrate: For the Monster Hunt single-player missions in The Witchwood, what percentage of the cards you see will be from the new expansion?

Dave Kosak: We try to heavily weight towards the set, but because there's just so many cards you need to make a deck with, Monster Hunt plays Wild, like everything is open season. I don't know what percentage, off-hand. Big enough to make an impact.

But it does give us an opportunity to kind of tell the story of The Witchwood. So a lot of the collectible cards are also monsters that you fight, as well as some unique monsters that are just for the monster hunt mode, and they interact with the monster hunters, and you kind of get some cool dialogue and some flavor, to tell the story of The Witchwood. And the story of Hagatha, the big bad boss that we teased in the announcement video. Hagatha will play a big role in The Witchwood.

GC: So the Year of the Mammoth is coming to an end. Do you personally have any favorite decks from the past year?

DK: I was a huge fan of Dragon Priest. And my favorite was...Drakonid Operative. I can never remember the name, because to me he's just "Secret agent, coming through!" Drakonoid Operative was a really good one, he's rotating out, but I still think Dragon Priest is going to be viable, so I'm going to try to make it work. We'll see.

Dean Ayala: I like a lot of the Old Gods decks, N'Zoth, even the C'Thun stuff that I played for a long time, and I would continue to try to make work, and Yogg-Saron. I play a fair amount of Big Priest, and nowadays Y'Shaarj is a huge part of the deck, so him leaving the fold is a big deal there. Plus I feel like the Old Gods were cool, and like a flavor hit for that set, and sort of evolved over time. At first everyone was playing C'Thun, then everyone was playing Yogg-Saron, then everyone was playing N'Zoth, and then Yogg-Saron starts to show up and they sort of cycle back through.

DK: Jade is also rotating out, and that's kind of a big archetype there. So it will be a big change.

GC: How often do dominant decks or strategies surprise you?

DA: Only one time that I can remember in the history of working on Hearthstone balance, which is like from Naxxramas, has there been a deck where it was like, "Oh we just never conceived of that deck," and that was recently, Dead Man's Hand Warrior, that cycles through their entire deck and has an infinite amount of cards with two Dead Man's Hands. It was actually really scary, because I remember watching a Twitch stream and being like, "Oh my god...we didn't playtest this! I hope this doesn't go horribly wrong."

But we've nerfed cards in the past, so clearly some of that is surprise, right? Because if we could not have done a lot of those things, we wouldn't have, like with Undertaker, Corridor Creeper, and Patches is an example.

DK: Patches had a good run though! You could use him most of the Year of the Mammoth before we put him in his place.

DA: There's some cards like that. I think having Yogg-Saron the way Yogg-Saron was, for the amount of time he had his sort of mechanic before we changed it, that's probably one of the only nerfs where I don't regret making it in the first place. Like having him the way he was for that amount of time was actually pretty positive, and there was a lot of fun that came out of it.

GC: Talking about nerfing a card, what goes into a decision like that? You go on reddit, and you'll see people saying "They should have nerfed this, why did they nerf that?" So how do you decide what needs to be nerfed?

DA: There's a variety of different things. We look at a lot of data to try to understand what's going on. The thing the data is the best at is that it shows us how likely this problem or not-problem is to continue, or not. So a lot of times you'll have something that's very unpopular community-wise, and is also very powerful, and that tells us that this is a problem that's probably not going to go away anytime soon.

Whereas if there is something that is a perceived problem but it isn't actually that powerful in the background, you know when we have data that it's a 47% win rate or whatever, or there are a lot of meaningful counters to the deck, we tend to let those stories play out, because players are smart, especially given the pace of the game, and eventually you sort of figure out what's good against any individual thing.

So I think those two things are really the biggest ones. Perception is the most important issue, though. With Patron Warrior, I think we were kind of wrong, in that it was perceived that this deck was very powerful and it was un-fun to play against, but it was never a very powerful deck through data, but it never went away, so eventually we felt like we had to make a change.

I think there are some games out there where their philosophy is that you make changes in order to switch things up. That's not really our philosophy. We're such an evolving meta-game, and it's part of the thing that makes Hearthstone fun is that there are all kinds of players out there that are trying to figure out where the meta lies, these are the popular decks, how do I use my knowledge of Hearthstone and my own creativity to build something that's going to do well in this environment?

I think when you start changing things over and over again, it becomes less of a situation where you are trying to figure out the new thing on your own as a community, and just waiting and going "Okay this is a powerful thing, let's wait until Blizzard changes that, and then we'll see what the next powerful thing is." So I think it's important to us to let the community try to figure out things, until we feel like we are in a situation that is not going to be solved.

GC: Is keeping the game's different classes balanced a goal, or is it more of a rotating spotlight from one expansion to the next?

DA: It's certainly not a rotating spotlight with different expansions. That's a perception that happens from the outside, because I think that you get into situations sometimes where you have all these classes and they have varying degrees of power. Like Warlock is very powerful right now, so it's unlikely that we will continue to support a very powerful Warlock archetype, whereas a deck like Control Shaman or something is not very powerful right now, so maybe we want to give some more tools to it. So I think naturally when you're making all these adjustments and not trying to support something and trying to support something else and sort of bring them to a realistic similar power level, naturally you're never going to hit exactly on those things, so sometimes it can appear like "This person gets this thing this time, and this person gets this other thing the next time."

Is the intention to create an equal power level across all classes? It's more like a perception of fun. I would say right now that, with Warrior, we're in a situation where the population size of Warrior is very low, but they have one deck that people are playing at a very high level, with Dead Man's Hand. They're cycling through their entire level and it's a really difficult deck to play, but it falls in line with the identity of Warrior. That class has a relatively low win rate, in data, but I think they're still in a pretty cool spot. They have some very high skill-cap decks to play, and there's some strategies that you can do there, and even though the population size is low and the win rate is sort of low, that's not necessarily reflective of Warrior not being fun. And if each class being fun is the end goal, then the population size and win rate doesn't really matter, as long as we're reaching, like, "This is fun."

DK: Correct me if I'm wrong, but it's more about giving every class fun stuff to do, and fun stuff to try, and lots of options, regardless of whether or not that's going to end up being a tier one deck.

GC: How do you guys feel about Valve getting into the digital card game territory?

DK: The genre is wide open. Getting more players player card games is awesome.

DA: It's great. I love Valve, and Valve games, and I think anyone really getting into the space is cool. Definitely no negative thoughts about it.