Of the three standard MMO classes, Healing is the only one that gives me little cause for comment. This is for several reasons. First, unlike the DPS or the Tank, there is no real world equivalent to the MMO Healer. The Healer is a work of pure fiction, developed solely from the fantasy genre. Games demand that characters on the point of death have the ability to quickly recover as
if they'd never been injured. This can only be explained through magical or supernatural means. The benefit this gives that no one really expects healing to be practical or based on the laws of science. Not even me. Instead, healing is bound by the specific background of the MMO world. This leads to the second benefit.
Because every game world has its own cosmology and cosmogony, healing can very
heavily from game to game. Unlike the DPS and Tank which are becoming more and more similar, varieties of Healers abound. In some games, the Healer doesn't even need to exist. Take for example, my own introduction to MMOs, Asheron's Call. That game had a very different focus on classes then most recent MMOs, and one thing it never had was a Healer. When a group got together, each
player was responsible for keeping his own character alive. This is probably partially due to the older group mechanics which made health monitoring all but impossible. Principally, however, it is based on AC's own healing dynamic. Most players carry around large numbers of healing kits which they can activate in or out of combat. In combat the kits are more prone to fail, but the intelligent player knows at what health level to start healing in order to stay alive. While healing kits aren't some sort of high magical form, the resulting health generation does not comport with real world standards so I would still place it in the magical category. Mage characters have a more "supernatural" method of healing through Life Magic (I say mage characters because melee and ranged warriors don't use wands in combat despite the prevalence of Life Magic.
A healing kit or a Life Magic spell could be applied to another character, but this is rare.
In contrast, Warcraft has a much purer version of the Healer. This model was followed by several earlier games such as EQ and DAoC, but not having played either I won't give specifics for them. In WoW, healing is a full time job. This is despite the fact that most classes have some ability to magically heal (and every one has access to non-combat First Aid). In solo play, Healers function much like any other class in a manner somewhat akin to AC, though they may have greater problems causing damage. However, in group actions Healers become critical. A group needs to be several levels above a dungeon's difficulty to operate without a devoted Healer.
Although it is in many ways a mirror to WoW, LOTRO has a different take on the Healer role. In most situations, healing is conducted by individual players for themselves. Unlike WoW, there seems to be an expectation that players will even use it during group combat instead of relying solely on the Healer to keep them alive. In leveling dungeons there is not generally the need for a designated healer. As I grouped for LOTRO,
I never heard the clarion cry of WoW "Need Healer!" It was just, "LF1M" (Looking for 1 more) because the specific class didn't matter. That being said, LOTRO does have a healing class with the Minstrel and a half-way healing class with the Captain. The Moria expansion also added the Rune-Keeper to that list. I understand there is a much greater need for healers in the end-game dungeons which
make the rare minstrel highly in demand (I moved on shortly after hitting 40, so never experienced this personally). All three classes are much more than healers, however. They are also skilled at providing long and short term buffs and are viable in combat in their own right as compared with WoW's Holy Priest, Restoration Druid, or Restoration Shaman.
Warhammer Online took an interesting approach for Healers as well. Some
WOW Gold was released in 2000 and is part of the WOW Hits series.