Actually, as it stands (for v18), the promotion Medic 1 is unavailable. Medic 1 requires Herbal Cures, which is only available to Health Care Units. But Health Care units cannot build Combat 1 or Drill1, one of which is a pre-reqs for Medic 1.
I edited C2C\Assets\XML\CIV4PromotionsInfo.xml, and added Health care units (UNITCOMBAT_HEALTH_CARE) for Combat 1 and Drill 1.
This does not solve your problem of March, but at least it allows you to build better healers.
An option for enabling March is, in the file C2C\Assets\Modules\OrionMods\GreatDoctorHealthCareMod\HC_CIV4PromotionsInfo.xml, find the entry for PROMOTION_MEDIC1. You'll see the entry for HERBAL_CURES as a requirement and COMBAT1 or DRILL1 as an option. You could replace either DRILL or COMBAT with the HERBAL_CURES, so that a unit would require Herbal OR combat/drill for Medic 1. Medic 1 will open March.