Destiny's combat system doesn't justify the addition of a healing subclass. In RPG's and MMO's, healing abilities are there to ensure party members don't die when taking sustained damage from a mob. In Destiny, however, you don't fight that way. Destiny has no threat tables for mobs, and health regenerates in combat if you take cover for a few seconds. What exactly would be the point of a healing class when you can heal passively by not taking damage for about 4 seconds? Also, the Sunsinger subclass does exactly what it was designed to do - generate Orbs for your fireteam and provide the player with more survival abilities as compared to Voidwalker. The Flame Shield ability is a great example of this, as is the Radiant Skin perk. This, coupled with the ability to carry two Solar grenades provides excellent zoning potential, essentially blocking enemies from progressing through choke-points or preventing melee enemies from touching you for a short time.