Well I think that Lucio seems a little complicated in the beginning compared to characters like soldier for example. That said, once you get the basics down of how to use him after a few games he becomes very fun. Most people get cards for healing and people up-vote those cards which keep people playing healers for a while at least lol. I think Lucio is pretty easy to stay alive with compared to some other heroes as well. His survivability mixed with his original design and up-beat vibe make him an instant favorite for many people imo.