Yeah, guess either SSR healer would really complete your team. Bozel from the current focus banner could be the caster you’re looking for, though the free Bozel event might return in a few months.
In particular, Bozel’s sleep skill got me through this week’s A ultimate trial. I guess Bernhardt’s shield bash might work too, but Bozel has better mobility and better range on sleep. He was also instrumental to beating Aniki Rocky for me.