>>534065953
You're placing too much importance on elemental weakness.
And too little focus on who is great at strengthening who.
1. Your main DPS aligning against opponent weakness is usually good enough.
2. The remaining 2 slots should be concerned about "how well can we synrgise the main DPS?"
In your case you av completely misplaced Vivian even though the -anti-Ether alignment is "correct", her synrgy to Yanagi is Even More correct.