I find that as I scroll through this subreddit, most people have complaints about the cards that are easily overleveled (RG, Elite Barbs) and the ones that are overpowered (Executioner pre-nerf, Electro Wizard). And while these are fair complaints, I have found that the game's balance is hindered most by low cost elixir cards that provide more value than they should for their cost.
It is my opinion that a card's cost, not its rarity, should determine the strength of a card. For example, a Wizard should be a stronger unit that an Ice or Electro Wizard because it costs 5 elixir rather than 3 or 4. Where rarity comes into play is with extremely unique functionality that makes the card significantly different from its alternatives. Unfortunately, there are too many cards in the game that cost less than alternatives and are nearly as strong as these alternatives.
A few examples of these power creeped unit groups: Skeletons currently outshine both Guards and 2 elixir Goblins; Goblin Gang has made 2 elixir Goblins and Spear Goblins obsolete; Musketeer and Electro Wizard cost less than Wizard or Witch but is almost always more useful (because splash spells are significantly more useful than splash troops); Knight costs less than Valkyrie, Lumberjack, Mini PEKKA, Prince and Giant Skeleton and offers "jack of all trade" versatility; Cannon is 1 less elixir than Tesla and provides more value because of how similar the two cards are.
Let's take Knight as an example: the card isn't noticeably overpowered, but he offers a little bit of everything that makes him more reliable than any of his melee troop substitutes. His hitpoints are extremely close to Valkyrie's, and his damage per second is actually superior to Valkyrie's. His 3 elixir cost makes him significantly better than Giant Skeleton, who has worse DPS and barely does more damage per hit; his only benefit over Knight is his death damage, which rarely hits the cards around it because of the 3 second bomb time. Knight is also a decent answer to tankier units, which removes some of the value from Lumberjack and Mini PEKKA, especially because his 3 elixir cost allows a player to play additional cheap defensive units to counter said units. He does a decent job of defending win conditions like Graveyard, Hog Rider, and Giant, and he is extremely useful in countering support units like Musketeer and Electro Wizard.
To be clear, the purpose of this post is to shed light on the issue of power creeping, and how there are numerous examples of it in the game that prevent the meta from being fully diverse. While the current meta is extremely diverse in terms of spells and win conditions, the support units are very limited because these support units completely outshadow their competition. Cards like Skeletons, Knight and Electro Wizard are significantly better than more expensive alternatives because of their cheaper cost, and bargain packs like Goblin Gang and Skeleton Army make cheaper alternatives less useful because they provide slightly more risk but considerably more value.
In future balance changes, I hope that the Clash Royale team can see the issue with these cheap units and nerf the cards that replace the need to play other units. Cards like Ice Golem and Mega Minion were once overpowered, but have been nerfed to the point where they are unique cards that do not provide too much value for their cost. By following this pattern, Clash Royale can help other cards shine that currently never see playing time, not because they aren't well designed, but because other cards provide significantly more value.
One approach to doing this is to give every troop a unique purpose in the game. For example, if Electro Wizard does tons of damage AND provides significant control ability, the card is clearly stronger than it should be for its cost, especially when compared to more expensive cards. By focusing on one of its roles, such as its ability to control, and nerfing his damage per hit, the developers can give Electro Wizard a niche functionality while allowing other cards with higher damage and DPS or splash ability to shine a little more.
This post was created to start a discussion about these issues that hopefully Clash Royale developers can address in future balance changes and when designing future cards, so if you have any ideas about cards that provide too much value for their cost and ideas on how to limit their effectiveness, please feel free to mention them in the comments. If you disagree with the post entirely, please let me know why; I always appreciate constructive criticism.
As with all of my posts in this subreddit, I simply wish to make the game as fun as possible, and by creating diversity in any meta by maintaining a balance of roles with win conditions, spells, buildings, and support units, the game will be at its best. Best of luck to everyone, I hope to see you in the arena!