I always thought of SCH as the "dark" healer. Just look at their DPS skills. Bio and Bio II which are poisons, Miasma and Miasma II which are both based on choking darkness, Shadowflare, Ruin and Ruin II, Energy Drain, Virus. Their heals are kind of philosophy/science based as well: Physick, Adloquium, Succor, Lustrate, Indominability... The only things that really dispel the dark/anti-holy theme are the fairies and Sacred Soil.