The Below should make it back to normal heal damage. Not sure though, didn't test it.
In Battle.c find:
switch (skill_id)
{ //Calc base damage according to skill
case AL_HEAL:
case PR_BENEDICTIO:
case PR_SANCTUARY:
/**
* Arch Bishop
**/
case AB_HIGHNESSHEAL:
ad.damage = skill_calc_heal(src, target, skill_id, skill_lv, false);
break;
And then add
ad.damage = ( skill_calc_heal(src, target, skill_id, skill_lv, false) / 5);
Below AL_HEAL, so should look like:
switch (skill_id)
{ //Calc base damage according to skill
case AL_HEAL:
ad.damage = ( skill_calc_heal(src, target, skill_id, skill_lv, false) / 2 );
case PR_BENEDICTIO:
case PR_SANCTUARY:
/**
* Arch Bishop
**/
case AB_HIGHNESSHEAL:
ad.damage = skill_calc_heal(src, target, skill_id, skill_lv, false);
break;