Designing a good card is a shared goal for stakeholders of a card game but different people will have their own definitions as to what constitutes good design. Before I give my own take on it let me tell you what I think doesn't define how well a card is designed, numbers.

I think a lot of reddit hearthstone players consider a well designed card to be a card that exists in playable meta decks but doesn't result in an insane win rate when played. An often cited example is Azure Drake for the way it was ubiquitous in decks back in the day but didn't outright swing the game on the turn it came down. However I think that definition leans more towards a well balanced card which to me, is circumstancial. The exact numbers on a card can theoretically be tweaked as many times after release and many cards could be nudged into this state. Certainly, there are cards that are made in a way that makes it difficult to balance and a more 'balance-able' card does speak to it's design but I don't think it's the primary metric that should be used.

Decisions

I think a well designed card primarily hinges on the amount of interesting decision making that revolves around said card. Decision making is what separates games as a medium to something more passive like watching a movie. The more interesting decisions that players can make with a card whether it be from the hand, the board or during deck building, the more fun it contributes to the playing experience as a whole, and cards should be designed to facilitate this. Not only is decision making fun, it also means

• The better player can make more correct decisions to squeeze out a higher win rate.
• More decisions offered to both players means players feel like they have higher agency on the outcome of the game, resulting in less losses where it feels like there was nothing you could've possibly done. Personally I don't mind losing if I was offered choices but lost because I failed to make enough correct ones.

With that being laid out, I want to examine Azure Drake again. Does Azure Drake push a lot of interesting decision making? Not as much as you'd think from it's text I think. If you had this on turn 5 you'd just drop it for the body and cycle, at 5 mana you would rarely save it to combo for the spell damage. Similarly drawing is a decision to pay an upfront cost with the possibility of making a better play with less mana but at 5 mana this was rarely the way it was used. From your opponent's perspective, there's a decision to trade or ignore the 4/4 with spell damage but that's about the extent of decision making revolving this card.

A card that is worded similarly to Azure Drake but I think is better designed is Blood Mage Thalnos.

The difference is that this card is much cheaper and the draw happens on death rather than on play. At 2 mana there is an actual choice on whether to play this for cycle or to combo with something like Backstab (It's still skewed towards cycle but not as heavily as Azure Drake). Since the draw doesn't happen immediately, your cycle hinges on your opponent clearing it or playing something you can run it into. Both players have agency to control the timing of the draw whilst weighing the threat/value of spell damage.

Given this definition here are two cards that I personally think are pretty well designed in Standard right now.

Ultralisk Cavern

On it's own this card is already kinda interesting. It's a 1 damage aoe so you have to combine it with some other damage source to meaningfully clear various board states. The damage is separated into charges with a 1 turn cooldown so a full clear with Eternal Layover is well telegraphed to both players. You also have reduced board space and the nuance of locations blocking adjacent effects.

Then you can consider Consume (uses 1 durability from the location to heal your character by 8), which staggers the threat of a giant but also uses charges which means the opponent can pressure the use of a heal to in turn reduce the threat of a board clear. Eternal Layover itself has a ton of choices to be made with Ancient of Yore. Deckless Warlock is a really cool deck.

Kil'jaeden

Okay here me out guys. If Ultralisk Cavern was an example of fun micro decisions, Kil'jaeden is a macro one. In the control mirror you don't always want to drop Kil'jaeden as fast as possible. For example against Death Knight (in the year of the Raptor), they have multiple ways of stealing minions or full clearing the board such that a singular demon with big stats just won't cut it. You want to Kil'jaeden as soon as you have enough control tools of your own but still faster than your opponent.

When you drop this you force a decision on your opponent. They can either pivot to a game plan that kills you fast enough, or chase with their own Kil'jaeden once they feel like they have enough resources in hand.

The trade off for this card existing is that it completely negates fatigue as a resource which is a valid argument. Though I think the decisions revolving Kil'Jaeden existing is a funner experience than players slowing the pace of the game to not dig into fatigue, personal preference. Also beeg number go up.