SKiLLsSoLoN

Well the Priest Pocket Healer was made for just 2 people. It was to be a follower only type of FightClass.

I can help you some, I made one that worked in both party and raid but i'm not willing to share it all. I used LUA. Here is a simple:

<?xml version="1.0" encoding="utf-16"?>
<FightClass xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <FightClassGeneralSettings>
    <FightClassName>Chainhealer</FightClassName>
    <Range>30</Range>
    <FramePerSecond>90</FramePerSecond>
  </FightClassGeneralSettings>
  <FightClassSpells>
    <FightClassSpell>
      <FightClassConditions />
      <SpellName>
PQR_CustomTarget = "player"
PQR_CustomTargetHP = 100 * UnitHealth("player") / UnitHealthMax("player")
local group = "party"
local members = GetNumPartyMembers()
lowhpmembers = 0

if GetNumRaidMembers() > 0 then
  group = "raid"
  members = GetNumRaidMembers()
end

for i = 1, members, 1 do
  local member = group..tostring(i)
  local memberhp = 100 * UnitHealth(member) / UnitHealthMax(member)
  if UnitInRange(member) 
  and UnitIsFriend("player", member)
  and UnitIsDeadOrGhost(member) == nil  then
    if UnitGroupRolesAssigned(member) == "TANK" then memberhp = memberhp - 1 end
    if UnitThreatSituation(member) == 3 then memberhp = memberhp - 3 end
    if memberhp < 85 then lowhpmembers = lowhpmembers +1 end
    if memberhp < PQR_CustomTargetHP then
      PQR_CustomTarget = member
      PQR_CustomTargetHP = memberhp
    end
  end
end
        
if PQR_CustomTargetHP < 80 
then
	CastSpellByName("Geringe Welle der Heilung",PQR_CustomTarget)
end
        
</SpellName>
      <Priority>7</Priority>
      <CombatOnly>false</CombatOnly>
      <Timer>2500</Timer>
      <NotSpellIsLuaScript>true</NotSpellIsLuaScript>
      <CanMoveDuringCast>No</CanMoveDuringCast>
    </FightClassSpell>
    
  </FightClassSpells>
</FightClass>

I created it using PQR. So it has some PQR related stuff in it ^_^

I have my client in German (Best language imo). 

This is about all the help i'm giving. This is a lot because it will look at the lowest HP target which is named PQR_CustomTarget and if they are below 80% it will cast Geringe Welle der Heilung (Lesser Healing Wave). Also the  lowhpmembers count is made for AoE healing like Chain Heal.

I hope this helps. LUA healing is the best imo. But I never got into the C# code of this program, so I could be wrong.