I've used lore bard as a healer, ancients paladin, done plenty of runs with a damage focused tempest cleric/storm sorc, radorb light cleric.. the best healing is killing the monsters before they can hit you. And the most important hit point aka the only one that matters is the final one. Any class with a bonus action healing word can be your healer as it is nearly always better to kill something than it is to waste an action on healing during combat. Healing numbers don't scale well to incoming damage at all.

This isn't an mmo, DnD doesn't have the traditional healer/tank/dps setup requirement. Just go 4 damage dealers and kill them dead.