Comfey, Clawitzer, or Tapu Fini
I picked Comfey due to it having the ability Triage giving off priority healing (+3 priority is insane) I also picked Clawitzer because it has the ability Mega Launcher which let its heal pulse to heal 3/4 of an ally's max hp. Tapu Fini has Misty Surge and good support moves. So it really depends if you want more healing, status immunity, or priority healing.
Clawitzer @ Aguav Berry
Ability: Mega Launcher
EVs: 4 HP / 252 Def / 252 SpD
Careful Nature
- Heal Pulse
- Helping Hand
- Flip Turn
- Icy Wind
Comfey @ Focus Sash
Ability: Triage
EVs: 252 HP / 128 Def / 128 SpD
Bold Nature
- Floral Healing
- Giga Drain
- Helping Hand
- Aromatherapy
Tapu Fini @ Misty Seed
Ability: Misty Surge
EVs: 248 HP / 124 Def / 8 SpA / 128 SpD
Calm Nature
- Light Screen
- Heal Pulse
- Reflect
- Icy Wind
Here are some other options for them
Comfey: Defog, Heal Bell, Tailwind, Synthesis, Tailwind, Taunt, Ally Switch, Light Screen, Trick Room, and Charm
Clawitzer: Aqua Jet and Muddy Water
Tapu Fini: Scald, Muddy Water, Taunt, and Soak
(You would want to change some of the EVs for some of these other moves)
Also, I assumed these would be support Pokemon.