No one can rival hokage tsunade in healing large groups. However, her usability in one on one fights is very limited. Her sannin war counterpart is very versatile in that regard. Being able to heal twice and attack three times or heal and apply immunity to debuffs depending on the breakthroughs that are active. A close second would be summer sakura though she would need a very high HP in order to be an unstoppable healing tank.

Obviously Water main. Sakura Summer is awesome as well but not for group heal.

Okay, and what about sakura cloak/sailor?

Water main doesnt count

She had her time in the spotlight but us now overshadowed by summer sakura and SB tsunade. Maybe if she gets her own SB she could make a comeback but for now I stand by what I said earlier.

- Young Tsunade can heal multiple, but 100 chakra required.

Much cheaper than Kage Tsuna, rarely see her in battle because of conditions requirement.

- Summer Sakura can heal 1 (or 2) unit across team. If you let her lives pass round 3, her slugs are everywhere.

Con. she can get blitz round 1 from Hiruzen etc.