Should a Medic shoot big ZEDs on Hell on Earth?

No. Shooting can aggro a Scrake or Fleshpound onto you. Shoot only small ZEDs sneaking up on the team that nobody else is handling.

Which perk skills does the guide recommend?

All skills from the left branch, which strengthen the team and keep the Medic alive; a combat Medic is said to be of little use.

How can you heal three people at once?

Heal with alt-fire from three different weapons in rotation: fire alt-fire on one weapon, switch, fire again, so three darts are recharging at once.

Perks & Classes

KF2 Medic on Hell on Earth: Keeping the Team Alive (Russian Guide)

This is a translation and paraphrase of a Russian guide aimed at Medics who struggle on Hell on Earth. A good Medic does several things at once: does not die, does not let teammates die, judges the threat level and acts accordingly, remembers the team's future depends on the Medic, and does not panic.

The basics

Weapons are a matter of taste, but the author recommends taking a rifle, a shotgun and a pistol.
To avoid dying, do not shoot ZEDs on Hell on Earth: if you aggro a Scrake or Fleshpound you will have problems. Shoot only small ZEDs that sneak up on your team and which nobody else can handle. Do not charge in like a kamikaze. Heal yourself constantly.
Skills: the best choice is to take every skill from the left branch. It greatly strengthens the team and keeps you from dying, and a combat Medic has very little use.

Medic character screen A level 24 Medic in the character screen of the Russian client.

How to play the Medic properly

Bind the alternate fire (heal) to a convenient key (the author uses Alt).
Learn to switch weapons fast and press the heal key constantly. For example, when you see a Commando at 50 percent health, tap heal on the rifle many times, switch to the pistol and tap heal, then switch back, and so on. You can heal three players at once from three different weapons.
Watch the team's health and look around all the time.
Falling back at the right time is your main task: a good Medic stays away from the melee and heals.
Do not shoot needlessly and do not get distracted. Shoot only when you are sure nobody on your team will die.
The most important part is throwing grenades correctly. Predict where a teammate who is being beaten by a Scrake or Fleshpound will be in 3-4 seconds and throw the grenade there. If he is pinned in a corner, throw three grenades at him and heal until the heal button breaks.
Do not fear a Scrake or Fleshpound running at you. Take the hit (ideally parrying with the knife) and run to a safe place.
Against the boss the tactics are the same.

ZED knocked into the air A ZED flung high into the air by a Medic weapon.

Final secrets

You can heal with the medkit on slot 4.
If you shoot the boss with the Medic shotgun, he runs away from you.

FAQ

Should a Medic shoot big ZEDs on Hell on Earth?: No. Shooting can aggro a Scrake or Fleshpound onto you. Shoot only small ZEDs sneaking up on the team that nobody else is handling.
Which perk skills does the guide recommend?: All skills from the left branch, which strengthen the team and keep the Medic alive; a combat Medic is said to be of little use.
How can you heal three people at once?: Heal with alt-fire from three different weapons in rotation: fire alt-fire on one weapon, switch, fire again, so three darts are recharging at once.