I think you have it flip flopped. Druids are often preferred in XP groups because they can port and their heals are more than enough (not to mention DS, and other buffs), although still considerably weaker than cleric's. Clerics are a must in raids due to HoTs and their powerful quick heal. I mention quick heal because they are extremely crucial in fights with high DPS mobs. Never will you find a druid main healing a raid unless you are raiding NDHK with a 8k+ warrior or something, and archaic slow/good slower.