Since the end of patch 10.3, the Dark Team has been dominating Teamfight Tactics. Besides having a strong effect, 5/6 members of the Dark Team are powerful carries, ensuring you will never lack damage when playing this composition. As long as you’re not too unlucky, 6 Dark units will be very strong with superior damage, compensating for their lack of tankiness since your opponents are likely to be eliminated beforehand, making additional tanks unnecessary.

Perhaps Riot Games made a mistake by ignoring the Dark units in the recent patch 10.4, as they continued to dominate Teamfight Tactics with unstoppable power. Thus, the release of patch 10.4b recently acts as a corrective measure from Riot Games, hitting hard on the damage output of the Dark team, especially late in the game.

Dark Team
Bonus damage at 6 units reduced from 165% to 150%.
Sion
Ability damage reduced from 200/400/800 to 200/350/700.
Master Yi
Bonus damage per attack after using Meditate reduced from 75/100/500 to 40/80/500.
These adjustments heavily impact the two phases where the Dark team is the strongest, which are mid and late game. Essentially, Sion is as crucial as Kindred in this composition, being both tanky and providing crowd control while also dealing significant damage. Nerfing Sion’s damage will make the Dark team more susceptible to being “broken through” as the shield won’t deal damage like before, giving opponents a greater chance to survive.

In the late game, the primary carry Master Yi has also seen a relative damage reduction, especially at 1 star. To be honest, you need to be very lucky to get a 2-star Master Yi as this swordsman is highly contested. Therefore, 1 star is the usual level for Master Yi, and a reduction of 35 damage per attack, along with the decreased amplification from the 6 Dark units, makes him considerably weaker.

In summary, the 6 Dark units after patch 10.4b will go from being an ultra-strong champion team to a composition that heavily relies on “luck” to secure a top spot. You must upgrade 3-cost units to 2 stars early or get Master Yi by level 7 to have a chance at the highest rankings. Otherwise, if you play as usual, you might end up in the top 4, but easily crushing opponents and claiming the top position will be a thing of the past.
