Healers in MMOs do some pretty cagey things - they inject their allies full of weird chemicals, suspicious herbs, surgical nano-probes or risky combat drugs to seal up their wounds and keep them in the fight.
When they're not pushing drugs, they're pushing their quirky religious beliefs and beseeching the fickle gods to restore their companions to health. And it doesn't matter whether or not the other characters belong to the same sect or cult or whatever - they get whatever the religious crazy person gives them.
My personal favorite MMO healers are the Minstrels of the Lord of the Rings Online, who use the incredible healing power of rock to keep their allies feeling good.
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Of course, LotRO also features the Rune-keeper, who uses the incredible healing power of rocks. Actually, the Rune-keeper's power is derived from his storytelling abilities rather than actual magic. The Rune-keeper spins tales of glory and hope to keep his allies' morale up. Perhaps "The Heroin Diaries: A Year in the Life of a Shattered Rock Star" by Nikki Sixx, or "Crazy From the Heat" by David Lee Roth, or "Shut Up and Give Me the Mic" by Dee Snider.