Dark Star
Riot Games has long recognized the weakness of the Dark Star trait, and they made significant changes in the mid-season update. Specifically, Riot has altered the trait’s effect once again, allowing units that are not part of the trait to still contribute damage to Dark Star units when they die. However, this is not enough as it does not change the nature of the Dark Star trait, where most of its units are extremely “useless”, perhaps except for Jhin and Xerath.
In reality, at this moment, there are plenty of ways to build a high-damage team, and you don’t need Dark Star to “one shot” opponents. The advice for you now is to never engage with or consider playing a Dark Star composition; the damage is not explosive, the composition lacks durability, and there is no clear strength.
Cosmic
The disappearance of Kassadin has had a more significant impact than many might think, as this unit was too powerful with the incredibly annoying effect of Wide Area Silence. When such a key damage dealer disappears, the position of the Cosmic trait gradually disappears entirely. Moreover, the meta is shifting towards burst damage, so the additional healing from Cosmic is of little use.
Therefore, the Cosmic trait has gone from being one of the most powerful traits to nothing more than a trap that leads players to fail miserably. Gamers are best advised to avoid this trait; it’s only a matter of time before the healing ability of Cosmic cannot withstand the massive damage from opponents.
Guardian
Following the craze of Aurelion Sol – Guardian, the balancing team of Teamfight Tactics nerfed this class, putting it into a real crisis. In fact, the decline of the Cosmic trait mentioned above has also weakened this class since its two key units, Xin Zhao and Rakan, belong to this trait. Historically, this class has always been overly reliant on the melee damage dealer, Xin Zhao, which makes it very easy to be controlled by frontline units.
Furthermore, as Riot Games adds more 2-3 cost units into Teamfight Tactics, the probability of rolling the correct unit you need decreases, requiring more gold to achieve 3-star units. This inadvertently makes rolling compositions like Guardians very difficult to reach their power peak early, such as with 3-star Xin Zhao or Rakan.