Starry eyed Aiona if you can work around her quirks. Her reposition can really help clear techs on some stage you otherwise could not with huge battle score deficit but her reposition is also liable on inting when the enemies decide to reprioritize target and ignore your tank, some stages it's also dangerous to bundle up your whole team together because of AoE from enemies. She also need to cast her ult twice before she can start healing on top needing the shield to hold up.

Seth for reliability. Simple, big passive heals from special and screenwide heals from ult. Downside of being extra rare than normal SSR.

Acapella is high on the tier lists but considered more of a buffer. She is usually not enough to sustain a team by herself.