The following Tribal - synergies have such a high likelihood of causing players to drop out of the top 4 in The Arena of Legends.
Warrior Seal
After the comprehensive nerfs in patch 11.23, Warriors are currently one of the worst tribes in The Arena of Legends. Essentially, Warriors still possess the inherent weaknesses of 'gold hacking' tribes, namely not providing specific stats to the team comp and being very weak in the late game. Furthermore, this tribe also lacks a 4 or 5-gold unit with enough damage potential to become the team's carry.

Indeed, champions like Miss Fortune or Gangplank can help you greatly in the mid-game, but by level 8, 4-5 gold units have significantly superior strength. Tahm Kench may be a good tanking unit, but to deal widespread damage and destroy the enemy team's composition, this champion cannot perform. Therefore, the Warrior tribe is gradually being abandoned by players and only used for a short period of time. This also makes the Warrior Seal very ineffective.
Fighter Seal
In essence, in season 6, Fighters don't differ much from before as they still rely heavily on health pools for advantage. Season 6 Fighters also prove to be incredibly powerful with abilities to deal damage like Trundle or annoying crowd control with Zac. However, the advice is you shouldn't use the Fighter Seal as it forces players to break their team compositions to activate the Fighter synergy.

Take for example a Recycle - Fighter composition with Trundle as the main champion, using the Fighter Seal will force you to replace some key units like Jayce, Janna, Ekko to reach the 4 Fighter threshold. Then you'll lose out on important tribal - synergy activations or beneficial effects from the aforementioned champions. This only weakens your team rather than making it stronger. So the advice here is not to take the Fighter Seal no matter what composition you're playing.
Guardian Seal
To be fair, after the recent buffs, the Guardian synergy has become much stronger and is no longer easily taken down by magic damage as before. However, using the Guardian Seal is a whole different story as we need to understand that most compositions using this synergy only take 2 champions. The two units usually favored are Leona and Braum because of their extremely powerful abilities. Taking the Guardian Seal also forces you to break your team composition and sacrifice strong units in the backline.

Furthermore, the upgrades related to the Guardian synergy are quite lackluster and don't really strengthen your team. So activating additional Guardian thresholds is unnecessary, especially when using Tribal - Synergies. Perhaps the only scenario you should take the Guardian Seal is when using a Galio-centric team and want to add a bit more armor to this champion.