Overwatch 2

This achievement isn't as bad as it sounds. You may end up getting it without even trying. The achievement asks you to heal five different teammates, each for 200 health for a total of 1000 health. The tanks have 500-600 health so they have plenty of lead way for this achievement. You can still heal 200 health on all the other characters but it may need multiple heals in order for you to do so. If you play safe and out of the reach of the enemies attacks, you should be able to consistently heal your team and yourself in case you get hurt. It's much easier too when your teammates are sticking as a group instead of being singled out. If you were to play in a party of decently skilled teammates, you should have very little problems.

Overwatch 2 Solution

What does the Caduceus Staff do?

The Caduceus Staff's healing function is bound to Mercy's Primary Fire which is by default. You must have the Caduceus Staff out to heal.
Mercy's Caduceus Staff is able to heal allies or boost their attacks (we will focus on healing allies.) She is able to heal any ally within 15 meters at 55 health per second. This will cast a yellow beam (from you to the target) which will give away your position.
Her ultimate, Valkyrie, will allow her to fly, increase the length of her healing (so she can heal from farther away), and will tether the healing beam to any nearby ally. It also gives you constant health regeneration, increasing your ability to survive.

How do I unlock Group Health Plan?

Teams are made of 5 people (you included) so you will need to restore 150 health to all of your allies. Since you must do this without dying, positioning is key. Try to stay near the team and out of sight of the enemies.
Try to be aware of any flankers. If you take damage, retreat and allow your health to regenerate (this is a passive skill for Supports.) Remember that you have the Caduceus Blaster (it does 20 damage/.2 seconds.)

Valkyrie is the key as it enhances your healing and your ability to survive (some details above). In Valkyrie state, beware of Cassidy's High Noon and Soldier: 76's Tactical Visor as well as snipers like Widowmaker and Hanzo.

How do I boost this achievement?

The Group Method

1. Form a group with your friends and enter a match.
2. Choose Mercy and have your friends choose their roles.
3. Allow them to take 150+ damage and heal them. Rinse and repeat with each person.

The Lockdown Method

This is the most common method to boost Overwatch that requires 10 people.

1. Get a group of 10 people.
2. Get into two groups of 5
3. Disable cross play
4. Queue for Quick Play Open Queue at the same time and hope it matches you guys up
5. Once you match up, have someone from the other team damage your teammates for 200 health and heal them. Rinse and repeat with all 4 of your teammates.

Remember to keep the objective contested unless it's a Control map which will not need contesting unless someone captured it.

Mercy's Caduceus Staff ability allows her to heal her teammates at a rate of 50 health/second using a yellow beam from the staff.

This achievement comes down to you surviving for long enough get enough health restored. Just use your staff on your teammates as they get injured to heal them. If you're able to heal all 5 members of your team (not including yourself) for a total of 200 health each, the achievement will unlock.

You can check the bottom of your personal scoreboard at any time to see how much healing you've done total in the match.

If you'd like to learn more about Mercy, you can view this video. The achievement is described and shown at 9:08: