I never said you were limited. Are you suggesting that there is no more single-party content?
If one out of six of DD jobs aren't exactly what you need, then your losses are <17% at max. If your healer is geared toward AoE heals (as someone suggested earler), or healing over time, but the mob is doing spike damage on one player, then there's really only one option. I don't see how that's funny. >.>;
I don't think it's okay for DD or tanks either, but this topic was on the creation of new healing jobs, rather than the balance of old jobs.
I addressed single-party content only--you already called me out on that yourself.With large-scale raids, it really doesn't matter how your healers work; if you have only low-potency healers, the quantity can make up for a lack of high-volume healers. If you have a lot of high-potency healing, they can spread out and kind of accomplish the same thing. Of course there could be an advantage to having different healers with different strengths, but I don't see it as essential for a raid as they're all serving the exact same purpose of regenerating HP.
With DPS, the different types are (at a basic level) ranged, magic, and melee. You could even consider sub-divisions such as piercing, slashing, blunt, etc, or combinations (if RDMs in XI were actually able to melee with En-spells in XI, Enhancement Shamans or Paladins (don't they get 10% light damage and some light magic?) in WoW). The mobs have several different defenses for each of those. Healing, at a base level, is always going to give someone their health back. En masse (i.e. a raid/endgame event), it doesn't really matter what denomination over what amount of time--100 every second will equal out to 500 every 5 seconds, etc, whereas different types of attacks will not necessarily balance out.
I think it's a good idea to invent multiple kinds of healing, but I don't see a plausible way to differentiate between them where either 1) they're all not doing EXACTLY the same thing or 2) one becomes the only option.
That said, there is already competition among DD classes, but I think that imbalance is something people typically complain about, not try to increase. Why should we create it among healing classes?
If someone was suggesting a job that reduced HP loss by some other mechanic than directly "Player regains XXX hp," I'd be all for it--such as a class that specialized in damage prevention.
EDIT: Zantetsuken suggested something like this above--this I could approve of.
I don't know that this was due to a lack of available options. I think a lot of people just don't WANT to tank or heal.