Quote from MaxMcCall

We work hard to make games of Hearthstone feel different from one game to the next. Making each class feel that it has a distinct identity separate from other classes is an important tool to ensure different kinds of games. The hero powers are the strongest sources of class identity, but if each class used all the same cards, games would still end up feeling too similar to one another. (We’ve seen this in the past: when strong neutral cards are played ubiquitously, people enjoy Hearthstone less.)So, we try to give cards to each class that are thematically and mechanically different. There is still some overlap, of course. Multiple classes get deathrattle rewards – that is, cards that reward players for playing lots of deathrattle minions. Weapons are too central to Hearthstone to give to only one class, so about half the classes have access to them. Druids can attack with their hero, but they don’t have weapons. In return, Priests, Mages, and Warlocks have a slightly higher emphasis on spells than the weapon classes. Still, every class needs spells, especially some removal, so you occasionally see some bleeding with e.g. Arcane Shot and Holy Smite.We don’t highlight class flavor by exclusion very often. Hearthstone has few mechanics that aren’t core to its gameplay, so it’s tough to say ‘this class does not get this mechanic’ without paying a steep price. We do it a little – Hunter doesn’t get any healing, for example – but it’s tough to do en masse. Plus, defining things by omission isn’t very obvious.Instead, we try to promote class diversity by giving each class a few deckbuilding themes and supporting those themes with the class-specific cards in expansions. We’re more successful with some themes than others. Getting Warriors to build decks based around taunt minions has been tough, but Warlocks are generally happy to play decks based around Demons. Sometimes our themes are weak when we debut them, but gain strength as we make new cards over time. For example, Pirate decks were on the weak side until Mean Streets, but now plundering your opponents is very popular. Also, most classes have a class-specific mechanic, and most of those mechanics support deckbuilding rewards as well.Here are some of the loose themes we’ve tried to promote in the past. This list isn’t exhaustive, tends not to include decks that have existed since Classic, and we might do more or less of anything on here, but hopefully it gives you an idea:: Beasts, Tokens: Secrets, Deathrattle, Beasts (Druid Beast decks tend to reward a single large Beast, and Hunter Beast decks tend to reward having lots of Beasts): Spell rewards, Secrets: Buffs, Secrets: Healing, Shadowform, Deathrattle: Battlecry/combo rewards i.e. Shadowstep, Weapons, Stealth: Overload, Murlocs, Totems: Demons, discard: Armor, Enrage, TauntAgain, this doesn’t include decks that have always existed like Freeze Mage or Miracle Rogue – we don’t really need to make new cards for those decks to get people to play them. It also doesn't include 'neutral' themes like Dragons or Pirates.The main goal of these deckbuilding themes is to get people to build new types of decks. People don’t need much incentive to play the decks they are already playing, and frequently they are playing those decks because they are strong, which is why we try to promote new decks with each set, instead of reinforcing the existing metagame.