Remember that you can basically play every Catalyst hero with a short CD as a healer. Just use the craftable Catalyst that heals and gives you energy.
Mona or Ninguang are pretty good in that regard.
Obviously Mona even more because she is basically all support anyway, while Ninguang is a DPS/Burst beast that would benefit more from offensive weapons.
At a max refinement catalyst, you heal for 18% HP every 12-15 seconds, depending on which character ult you are using.
That's enough, most of the time.
Use the set that buffs party ATK by 20% for 10 second and you have close to 80% uptime on that too and someone who does actually help you improve your DPS, Barbara doesn't really do that after all unless you build her for attack and elemental reactions and use her as a Main Dps with a C6 Fischl (then she is actually insanely strong lol)
If you happen to play a sword-dude as Main DPS such as Ka$hing, you can use the BP weapon to heal your main character, since it's a very strong weapon anyway, even at refinement 1. Alongside the Catalyst ability, that's more than enough.
Mona scales with Energyrecharge btw. So lol @ that, she would probably the ideal character for such a support heal.