Karl brings forth tremendous offense and good damage uptime for the entire party. As the lead Adventurer, Slayer's Strength will allow Karl to quickly build up Strength stacks to swiftly finish the battle.
The combination of Yue's Defense co-ability and a multi-target damage Skill with Stun capabilities make for an excellent teammate. Given the relative ease of this battle, the downsides of Wild Instinct is sufficiently covered with Last Defense provided by How to Flee Properly and her passive.
Sinoa adds a random element to IO runs. Will she boost Defense, increasing team survivability, or will she boost Attack for quicker damage? It's a bit precarious, given she effectively takes the place of a second healer, but she'll be casting reliably thanks to Sleep res.
Halidom Grooms is added for additional Buff Time, while Jewels of the Sun provides a balanced mix of offense and Skill Haste. Bellathorna can be run in place of Halidom Grooms as well, and defensive Wyrmprints can be run in place of Jewels of the Sun if needed, such as How to Flee Properly or even Glorious Tempest.
Verica's the sole healer of this team and thus comes double-equipped with Recovery Potency Wyrmprints. Ark Voyager supplies an additional heal, but Otherworldly Bough is also an option that provides Verica with a self-targeted AoE. Regardless, her lack of Sleep Res isn't too much of a hindrance as a ranged Adventurer in this battle; bad timing may put her out when her heals are most needed, but the probability of failing a run due to this is fairly low.
Alternate Team Members
While sporting less overall offense compared to Karl, Naveed is well-suited for this battle on auto, as Radiant Bauble provides periodic Defense buffs and synergize greatly with Valiant Crown and The Heroes Arrive.
Ramona brings immense offensive and buff capabilities to the party, especially as a secondary AI. She excels greatly in combination with doublebuff effects as well, and is a natural shoe-in for Yue's spot if available.
Sarisse can easily replace Sinoa for more offense-focused support that is less RNG-reliant. Although Bow Adventurers may not fare as well in Imperial Onslaught, the sheer power of Brilliant Bolt allows Sarisse to provide a great source of spike damage as well.
If bringing in an additional healer, Vixel is the top choice. While Verica can function quite well already, the added security of Sleep Res guarantees uptime for Vixel. This is very important since his Spirited Song has a somewhat high SP cost, and he will want to cast Agitato Assault as much as possible to boost both his and Verica's healing.