Just Focusing on these two things here.
1. This is a damage centric MMO, you healing is designed to be pretty goddamn powerful to facilitate dealing as much damage as possible on healing classes, if you "just want to heal", I'd maybe suggest another MMO, or not playing healer, cos healers in this game are designed to deal damage. Doing more damage is the defacto way to improve yourself as there's no other valuable metric to judge by.
2. Ive seen this happen a handful of times in my many years with this game. The only time I see people leave at the start is some tanks auto leaven aurum vale, or people leaving when they inspect a tanks gear and see its an expansion out of date in the vault.