TL;DR: All cards will be highly unbalanced at some point in their lifetime. As some cards are more popular and well received than others, so will some cards that are not as popular and are hated and unused. Due to our own human perspective and flawed logic, we cause overpowered cards as well as underpowered cards.
The logic of syllogism states the following:
A = B
B = C
Therefore A = C
Most of the time, this is true:
Cows are mammals.
Mammals cannot fly;
Therefore, Cows cannot fly.
On the other hand, this may be untrue sometimes:
Penguins are birds.
Birds can fly;
Therefore, Penguins can fly.
We all know that penguins cannot fly. Due to this flaw in syllogism, it is not reliable as a basis of logical arguments.
Back to Clash Royale:
Relating this to Sparky, no one knew how to counter it. As it was a legendary, everyone had high expectations and saw that it could take out a tower within 10-15 seconds if left alone. You could say the relative thing to the Inferno Dragon, as many people complained that it was overpowered like Sparky, but now, people are asking for a buff. The reasoning behind our switched logic is due to the fact that cards like the latter are often expected highly of, but do not meet our expectations. As we do this, we are able to easily think of counters to this, hence the complaints.
On the other hand, elite barbarians and royal giant were not very highly acclaimed when announced as they were common cards. Royal giant, to many, was basically just a ranged giant that did minimal damage and was countered easily. Due to this original stereotype, few people used it, hence the buffs it received. Because of our own human, flawed logic, we have made royal giant into the monstrosity it is today. Same with elite barbarians. As it was a common card, we had little expectation for it, causing the low usage. Hence, Supercell, with its also human logic decided to buff it since no one was using it. Now, we are in the valley. As we complain that these cards are overpowered, we are not using the time to think of counters like we did for sparky and inferno dragon. Obviously, there are direct counters to every single card possible.
Now, back to logic:
Syllogism can actually be beneficial in some ways. Considering the fact that most of these cards are either leaked or shown by you tubers, we just about know what they will do. Here's where logic comes into play. Imagine the following scenario:
New card called Destroyer. One hits any tower, and takes 10 seconds to prepare the weapon.
Looking at our human flaws, we see "One hits any tower" and then we are completely blind to "takes 10 seconds to prepare the weapon." As we see the first part, we immediately panic and think the card is overpowered. But, once the card is actually released, everyone wants to get it so they can grind for the crown chest. As everyone uses the card, people will find counters to the card quite easily. Although there are many counters, Supercell will see the overusage of this card before the natural wave of counters to the card. They then will nerf the card, causing less and less people to use it. This problem occurred even before there were legendaries. Although X-Bow and Mortar were two cards of different rarity, and they were both originally in the game, they were used so often that Supercell had to nerf them to oblivion. Seeing the damage they caused, they gave them a minimal buff, enough to balance them.
Now, imagine this next scenario:
New card called Spiker. Deals one damage per second, but has a lot of health and can tank while dealing chip damage.
We see "Deals one damage per second" and basically give up on the card for its seemingly depressing attack. But, if only we had seen "has a lot of health and can tank while dealing chip damage." Seeing this, no one uses the card. As Supercell has continuously been doing balance changes due to popularity, they will likely buff the card to oblivion. This problem occurred to the Log. As it was a legendary, people were hyped for it, but seeing the low damage and incompatibilities it had when it was first release caused many people to drop the log in their decks and stick with zap. Supercell then continues to buff the Log to oblivion, until now, they have ALMOST found the balance point.
Logically speaking, all cards require the equilibrium that can only be managed by trial and error.
In reference to syllogism, consider the following:
Spiker has low damage.
Low damage means bad card.
Therefore, Spiker is a bad card.
Destroyer has high damage.
High damage means good card.
Therefore, Destroyer is a good card.
See? It's just logic! It's all in our minds.
The problem is, overpowered and underpowered cards are really just all in our minds; we make them overpowered by our low usage originally and then superbuffs to the cards. Vice versa with underpowered cards, high usage, and then supernerfs to the cards.
In conclusion, all cards will be highly unbalanced at some point in their lifetime. As some cards are more popular and well received than others, so will some cards that are not as popular and are hated and unused. Due to our own human perspective and flawed logic, we cause overpowered cards as well as underpowered cards.