>>531192330
Liter or Siren flipflop pretty evenly between being the better burst one, especially depending on the stage but generally yes, that is the premiere hard mode campaign pushing team. Siren can burst faster at the beginning of a stage and offers stuns which can delay problematic enemies from kicking your teeth in at the start of a fight, and if the stage necessitates more than two bursts, she can keep the burst chain rolling better than Liter

That said, attack buffs are by far the most important buffs in hard mode campaign for pushing deficits, so Liter can potentially let you cut through stages easier with the extra damage she gives. If you only need to burst twice, the disadvantage of needing to ramp up her CDR becomes less of a problem since you can usually just afford to wait the extra second or two and end the fight immediately with RH > Crown > RH. Overall though, it's very much dependant on the stage but they're pretty interchangeable. Siren is just a bit more forgiving and easier to use.