It seems the hero party was support-heavy. They have a healer, a white mage, and a tank. I guess it all helps the Hero shine.
And unlike in video games (where healer would quickly get bored with only heals), they have specialized, with healer doing only healing, and white mage doing buffing spells.
The real problem with the hero party, is that they were very mediocre individuals, who only managed to do what they did with the power of MC's support spells. In some other novels, they even make it sound like having support magic that is too good, is bad for the party members' growth.
Finally, MC does have decent heals, but they aren't as good as a healer buffed with his buffs.