Forecasting Arena Shifts by Class

Forecasting Arena Shifts by Class

As mentioned in the past, I love looking at data, and trying to use it to my advantage when possible. Hearthstone Replay officially made their collected data publicly available yesterday, much to my delight. I didn’t even know that this was planned for a release, but I knew data was collected through Hearthstone Decktracker, a tool I have used for years myself.  There’s lots of data about win rates for constructed decks in Standard and Wild, with great UI to see specific deck changes by deck. There’s also separate Arena data, which is what I was interested in the most, and will explore here.

Arena data

Not surprisingly, the Arena data has information about every single draftable card, as you’ll get a different deck each draft. These are the variables measured for each card:

  • Included in % of decks – What % of drafts have this card.
  • Copies  – Average copies of the card in each draft.
  • Deck winrate – Win% when card is in draft.
  • Times played – Raw times played.
  • Played winrate – Win% when card is played in game.


While having big data is great, it could be worse having data and misinterpreting it. Misinterpreting data leads to faulty reasoning and arguments. Let’s try to make some assumptions of this data before we proceed.

  • Players who use HS Decktracker are better Arena players than the average HS player.
    • HS Decktracker provides a ton of information in the game, which will allow the user to gain an advantage in getting intel. One could assume this helps, and the players who use it are more likely use other methods, like drafting tools.
  • Deck winrate and played winrate are independent by class.
    • As a class struggles, the overall winrates will plummet for the class. Just by looking at rates by class, we can see that Warrior and Druid are struggling a lot in the NA server over the last 14 days. Grimy Gadgeteer and Headcrack have the same deck winrate at 49.8%. One is a lot better than the other in reality, as Rogues win a lot more than Warriors.
  • Played winrate has bias depending on game situation.
    • I noticed that some pretty good cards had lower played winrates than expected. Flamestrike sits at 53.3%, the same winrate as Assassin’s Blade. Think about it this way, if you’re playing Flamestrike, chances are you are behind on the board. Mage players who choose not to, or don’t have to play Flamestrike likely have won already.
    • The same goes with card advantage cards. I often play card draw in a last ditch effort to draw into an out. This would skew card advantage cards to lower played winrates.
    • Pyroblast has a very high played winrate at 73.4%, but a 57% deck winrate. This signifies people playing Pyroblast to achieve lethal.


  • I’m going to look at the top 10 class cards for each class in deck winrate. It has been established that deck winrate is likely better at evaluating a card than played winrate.
  • I will only look at commons, rares, and epics. Legendaries are omitted as they show up too infrequently. Arena 7.1 put epics back on the map with higher offering rates.
  • I will omit undraftable cards included from old drafts.
  • I will seek to identify the cards that will be rotating out in the Arena once Journey to Un’Goro releases.
  • These data were collected on 4/3/17, approximately around 4pm EST.



  • Druid appears to be taking a huge blow to their Arena kit when TGT drops out. 7 cards in the top 10 will be leaving.
  • Without Mulch or any replacements in Un’Goro, Naturalize becomes the only Druid hard removal. While it becomes a better pick, it still isn’t great.
  • Shellshifter and Verdant Longneck are solid cards, but it isn’t enough help given what is dropping out.
  • Prediction: Druid might become one of the worst Arena classes.



  • Things are looking up for Hunter lately thanks to Arena 7.1. Also, none of the top 10 cards are dropping out.
  • Houndmaster is looking even better in the Beast meta.
  • Hunter gets some amazing early game cards and a seemingly premium early removal with Grievous Bite.
  • Prediction: Hunter gets more tools and isn’t losing much. Beasts will help the class even more.



  • Faceless Summoner and Forgotten Torch are undraftable cards, so ignore them here.
  • Mage will lose 2 cards in the top 10, Fallen Hero and Ethereal Conjurer. All the powerful spells are still here.
  • Primordial Glyph does the samething as Ethereal Conjurer albeit without the threat on board. A bunch of the other common cards are quite solid as well.
  • Prediction: Mage continues to be an Arena powerhouse. Elementals help bolster neutral minion picks.



  • Paladin loses Keeper of Uldaman, Argent Lance, and Seal of Champtions. These are 3 premium cards, but 3 out of 10 isn’t the worst.
  • Spikeridged Steed and Lost in the Jungle are solid gains.
  • Paladin also gainst other snowbally threats that are more win more.
  • Prediction: Paladin either stays the same or gets a little worse. In any case, it should remain in the middle of the pack, possibly still one of the better picks.



  • Priest loses nothing from their top 10 list in the upcoming rotation.
  • The loss of Dragons from rotated set would peg a card like Drakonid Operative a little. 5-mana 5/6 is still great to get though. Dragonfire Potion is still a board wipe to pick.
  • Priests get some Elemental synergy with Radiant Elemental and Crystalline Oracle. Shellraiser and Mirage Caller are pretty good as well.
  • Prediction: Priests remain in their current position as a strong Arena class. Fewer Potions of Madness will be a relief.



  • Undercity Valiant is not a draftable card, so it isn’t in this top 10.
  • Rogue loses a couple tools in Dark Iron Skulker, Buccaneer, and Shady Dealer. The class was propelled to #1 thanks to Arena 7.1, and Dark Iron Skulker was likely the culprit for that.
  • The new Rogue toolkit is very solid. Vilespine Slayer, despite being an epic, looks like an autodraft. Obsidan Shard, Hallucination, Biteweed are all solid.
  • Prediction: Rogue remains a top tier Arena class. SI:7 Agent (top deck winrate card) and tools are all still here to keep the class competitive. Lack of AoE didn’t kill the class before, and it won’t now.



  • Whirling Zap-o-matic isn’t a draftable card, so not included in this top 10.
  • Shaman loses none of it’s top 10 cards.
  • Shaman is going all in with Elemental synergy, and I believe this will benefit greatly with all the neutral Elemental cards. The minions are all unimpressive with their stats, so drafting synergy will be key.
  • Prediction: Shaman makes the leap from middle of the pack to top tier. The ability to curve out in the Arena with Elementals will weigh heavily on how well it will do. Some drafts could possibly stall out, if synergy breaks down.



  • Darkbomb isn’t a draftable card, so it doesn’t belong in this top 10 list.
  • Warlock loses 4 cards from this top 10 list, including Imp Gang Boss, Dark Peddler, Tiny Knight of Evil, and Wrathguard. Really, IGB and Dark Peddler are really bad to lose, as they are really, really good.
  • The new Warlock cards are definitely decent, with the minions being good stat sticks. Chittering Tunneler could be the new Dark Peddler.
  • Prediction: Warlocks get worse and will need to focus on increased minion-based combat with taunts. Could possibly be forced out of top tier status to the middle.



  • These are some putrid winrates. We are looking at the top 10 here!
  • Warrior loses a couple from this top 10, including Obsidian Destroyer, King’s Defender, and Alexstraza’s Champion.
  • Warrior gets very good minion help from Un’Goro, but nonexistent spell support. The three spells they get are nearly undraftable. Sudden Genesis is draftable but win more.
  • Prediction: Is it possible Warriors become even worse? Going forward, the strategy might just be to taunt up and draft weapons, as the spells are no good. That or just continue not playing Warrior.

Thanks to for all the data and screenshots!


Hearthstone Minion Averages and Radar Charts

My educational background and work experience thus far has allowed me to work with data all the time and has showed me how to evaluate things with numbers. While using numbers typically have a work or research-related application, numbers have been increasingly used to look at hobbies. I decided to look at some basic numbers with stats involving Hearthstone minions.

For this exercise, I just decided to look at averages for minion cost, attack, and health.

Hearthstone minions by class


What this tells you is that the average minion in Hearthstone is a 4 mana 3.5 / 4. The average neutral minion also has a similar cost and stat distribution as all overall cards.

It is pretty obvious that Druids have the highest cost minions, and biggest minions, consolidating their status as the ramp class. Rogue cards are the cheapest and have the lowest health. Shamans have a low attack total, tainted by 0-attack totems.

Hearthstone minions by set


The Basic set are clearly the weakest cards around, as they are the cards you get for free. Naxx and GvG were known for ushering aggro into dominance, as evidenced by their relatively low costs. BRM was a set that had a lot of beefy dragon minions.

Hearthstone minions by rarity


Finally, a view of rarity, which primarily has implications in the arena. You see a clear linear trend in the upward slope of cost, attack and health, as a card gets rarer.

Radar charts

I was doing some work on Microsoft Excel when I realized that Excel could create radar charts. Intrigued about this, I thought about what possible visual applications radar charts had on conveying information. This all led to me creating some Hearthstone-related radar charts.

For minions, I decided to categorize all class minions into “what they did.” To account for all the different types of effects, I had to put them into broad bins of what they did.

  • Spellpower – Pretty clear, e.g. Kobold Geomancer
  • Taunt – Pretty clear, e.g. Frostwolf Grunt
  • Damage – Something that deals extra damage, e.g. SI: 7 Agent
  • Charge – Pretty clear, e.g. Kor’kron Elite
  • Buff Self – Something that only helps itself, usually continuous, e.g. Lightwarden
  • Buff Other – Helps other minions, e.g. Blood Imp
  • Reinforcement – Summons something to the board, e.g. Dr. Boom
  • Cost Mod – Reduces or increases costs, e.g. Shadowfiend
  • Mana Mod – Affects mana crystals somehow, e.g. Grove Tender
  • Minion Mod – Affects minions in a non-damage way, e.g. Water Elemental
  • Hero Mod – Affects own heroes in a non-damage way, e.g. Fallen Hero
  • Cycle – Draws cards from deck, or gets you new cards in hand, e.g. Tomb Spider
  • Heal – Heals hero or minons, e.g. Earthen Ring Farseer


The graph of all classes is a mess, but if you look at individual classes, like Paladin, you see their minions focus on buffing each other (Argent Protector), and minion modification (Aldor Peacekeeper).


Also for minions, I looked at basic stat distribution, and classifying them as aggro minions (more attack than health), defensive minions (more health than attack), or even.


Very aggressive minions, those than have 2 or more attack than health are quite rare. You see Rogue class minions almost always have more attack than health or are even. Shamans and Warlocks have minions that typically have more health than attack.

Priests seemingly have no card that has 2 more attack than health.


Finally I made some graphs for the spells of Hearthstone, and what they do.


Paladin spells are primarily focused on buffs, and have all but one source of hard removal.


Meanwhile, Warlock spells are all about doing damage, but have some areas of decent hard removal and AOE.


All in all, this was just to help me learn to use radar charts to display visual data for Hearthstone. In the future, I may incorporate such charts when analyzing certain decks or even arena runs.