Best Team for Diona in Genshin Impact
Team #1: Morgana (Ganyu Freeze)
Ganyu takes advantage from the Freeze reaction, Cryo resonance and 4pc Blizzard Strayer to gain 55% Crit Rate (+20% from A1 passive = 75% Crit Rate on her charged attacks). She is the main damage dealer and her numbers get furtherly increased by Cryo swirl and her own passive talents. This team mostly uses Ganyu's burst as a main source of DPS together with Venti's, as both have quadratic scaling (more enemies hit = more damage). Note: Bosses can't be frozen, so this team is not effective against them.
Team #2: Eula Superconduct
Raiden is a top pick teammate for Eula. She enables Superconduct and provides constant off-field Electro application, batteries the team and acts as a second DPS (Eula+Raiden is also known as "Double DPS team"). Note: Raiden is forced into an ATK goblet build in this team, as she isn't getting any external ATK buff.
Xinyan works as a Sub DPS and shielder and provides Physical resistance shred through her shield and her C4, if owned. Xinyan's burst also gets a DPS Bonus in this team. This flexible slot can also host a Crowd Control character, such as Venti.