I already posted this on the latest community set design thread, but I figured I should make an own thread about it. It's pretty good advice if you want to make a custom expansion.
So, some few years ago I read this one article that really stuck with me. It's about the design process of Magic the Gathering. I'm pretty interested in game design and way back before Hearthstone was released I liked to create custom magic cards. This article really helped me going forward, but I've found it's very useful when designing Hearthstone cards as well.
It's a part of this series of articles (I really recommend you to read all of them), with this one specifically being about so called "Design Skeletons". It's basically a type of document that you make in order to plan out a set before actually creating the cards. This makes it easier to see the set of cards as a whole - to see if your set has coherent themes and mechanics. It's additionally a lot easier to reiterate and change cards when it's in text form, rather than making countless of different versions on Hearthcards.
A thing to keep in mind though is that Magic and Hearthstone are a whole lot different. So for you that don't know much about Magic, I'll explain a bit. In Magic there are five different colors that cards can have. Somewhat like the classes of Hearthstone, all of the colors have their own themes and mechanics. For example, red is a very aggressive color; black has a lot of graveyard manipulation and green has a lot of mana ramp and big creatures. Therefore you wouldn't really make a red counter-spell card, it doesn't really fit in with the theme.
Classes in Hearthstone on the other hand, aren't as much based on different playstyles. Of course Hunter is going to be more aggro oriented and Warrior is going to be more control oriented because of their Hero Powers, but as you've seen with cards such as Steamwheedle Sniper Blizzard are willing to explore more control oriented play styles even for Hunters. (Whether it works or not, they've at least tried...) But classes in Hearthstone are still all given their own mechanics and tools to work with, most even have class specific keywords.
With that in mind, when creating a set of cards - ask yourself what direction you want different classes to go in. What rarities do you want the cards to be? How will your expansion's mechanics be represented among them? Can you make the cards fit into a coherent theme?
Here's an example of a document I've made a while ago for an expansion named "Dungeons of Azeroth". I could have planned better, but the idea is to write down different mechanics you want to see for the different classes. You can start out pretty vaguely, such as "overload synergy card", or "cheap anti-aggro tool", or "secret counter". This is when you can think about how many control/aggro/midrange tools you give different classes, and how many spells vs minions you give them. Maybe you shouldn't give a class 7 spells and 2 minions, for example.
When the document gets more and more filled up, you will notice you have a much more specific/narrow goal for the whole expansion. The card creation process will go a lot smoother from there on and you can start making more concrete cards. Now you can focus more on the theme/visuals of your cards, as well as balancing and making sure the cards are actually fun. In the document, you can always easily double-check if your theme is coherent throughout all the cards and fix balance issues. Reiteration and change is a very important thing in design, so don't be afraid to change your cards if you think they will fit the theme better. Of course it's never a bad idea to keep back-ups of older designs, since they might still have some value to them.
I hope you found this post helpful. The articles go a lot more in depth and is a heck of a lot better written than this post, even though they're actually about Magic. So if you like designing Hearthstone cards, they will probably still provide you with some great advice.
Anyway, I hope you have a nice day and may your future Hearthstone creations flourish. :)
I'm glad someone else is highlighting the importance of planning and the ability to overlook your set. While I myself prefer a much more simple set skeleton than the one you presented I too work with a simple text file.
The set skeleton basics that I use can be found here: Set Skeleton Extended - Default This set skeleton is originally made for Magic the Gathering set but has been altered for Hearthstone design instead.
For comparison the set skeleton used for my Caverns of Time expansion (The one in my signature) can be found here: Set Skeleton Extended - CoT
Overall I like your points, and wish more people will see them!
I already posted this on the latest community set design thread, but I figured I should make an own thread about it. It's pretty good advice if you want to make a custom expansion.
So, some few years ago I read this one article that really stuck with me. It's about the design process of Magic the Gathering. I'm pretty interested in game design and way back before Hearthstone was released I liked to create custom magic cards. This article really helped me going forward, but I've found it's very useful when designing Hearthstone cards as well.
This is the article I'm talking about: http://magic.wizards.com/en/articles/archive/making-magic/nuts-bolts-design-skeleton-2010-02-15
It's a part of this series of articles (I really recommend you to read all of them), with this one specifically being about so called "Design Skeletons". It's basically a type of document that you make in order to plan out a set before actually creating the cards. This makes it easier to see the set of cards as a whole - to see if your set has coherent themes and mechanics. It's additionally a lot easier to reiterate and change cards when it's in text form, rather than making countless of different versions on Hearthcards.
A thing to keep in mind though is that Magic and Hearthstone are a whole lot different. So for you that don't know much about Magic, I'll explain a bit. In Magic there are five different colors that cards can have. Somewhat like the classes of Hearthstone, all of the colors have their own themes and mechanics. For example, red is a very aggressive color; black has a lot of graveyard manipulation and green has a lot of mana ramp and big creatures. Therefore you wouldn't really make a red counter-spell card, it doesn't really fit in with the theme.
Classes in Hearthstone on the other hand, aren't as much based on different playstyles. Of course Hunter is going to be more aggro oriented and Warrior is going to be more control oriented because of their Hero Powers, but as you've seen with cards such as Steamwheedle Sniper Blizzard are willing to explore more control oriented play styles even for Hunters. (Whether it works or not, they've at least tried...) But classes in Hearthstone are still all given their own mechanics and tools to work with, most even have class specific keywords.
With that in mind, when creating a set of cards - ask yourself what direction you want different classes to go in. What rarities do you want the cards to be? How will your expansion's mechanics be represented among them? Can you make the cards fit into a coherent theme?
Here's an example of a document I've made a while ago for an expansion named "Dungeons of Azeroth". I could have planned better, but the idea is to write down different mechanics you want to see for the different classes. You can start out pretty vaguely, such as "overload synergy card", or "cheap anti-aggro tool", or "secret counter". This is when you can think about how many control/aggro/midrange tools you give different classes, and how many spells vs minions you give them. Maybe you shouldn't give a class 7 spells and 2 minions, for example.
When the document gets more and more filled up, you will notice you have a much more specific/narrow goal for the whole expansion. The card creation process will go a lot smoother from there on and you can start making more concrete cards. Now you can focus more on the theme/visuals of your cards, as well as balancing and making sure the cards are actually fun. In the document, you can always easily double-check if your theme is coherent throughout all the cards and fix balance issues. Reiteration and change is a very important thing in design, so don't be afraid to change your cards if you think they will fit the theme better. Of course it's never a bad idea to keep back-ups of older designs, since they might still have some value to them.
I hope you found this post helpful. The articles go a lot more in depth and is a heck of a lot better written than this post, even though they're actually about Magic. So if you like designing Hearthstone cards, they will probably still provide you with some great advice.
Anyway, I hope you have a nice day and may your future Hearthstone creations flourish. :)