Although I am leaving myself open to accusations of bias again, I'd have to say my favourite healing class is the priest. He has such a wide variety of healing powers and such a deep bag of different tricks that, if given full choice, I'd take a holy priest over any of the other healing classes any day.
Priests have their weaknesses, such as how useless fade is, but their strengths more than make up for these short-falls. Being able to have a buff flying around the group, healing for a lot each time people take damage is wonderful, as is the fact it doesn't give the healer threat, it gives the threat to the healed.
Priests may have some longevity issues in a full-on melee situation, but every class will come to a point where they can't heal any more, and the priest will often have done a much better job at keeping everyone's health up before then.
With a priest I feel safe (until the priest proves to be bad at their class). If they're firing off a Prayer of Mending onto me before each pull I feel doubly safe. I have a priest here who knows their abilities and knows how easy it is to snatch agro on the pull with a few heals, so they're giving me the initial heal agro by making their first heal be a Prayer of Mending heal. The only other ability that comes close to doing this to my knowledge is Earth Shield, which is nowhere near as powerful as Prayer of Mending, from my tankish point of view.
Finally, a priest that doesn't know how and when to use their powerful abilities, such as Prayer of Mending, and/or whose gear isn't up to scratch could be a liability to the party, but you've still got a solid healer there and you can coax them into using their abilities properly.
All the time I was leveling my priest I was hearing about how paladins were the only healer worth taking anywhere. It made me a little upset that I had put all this effort in (and that there was still more effort to be put in) and that it would all be wasted. So it came as a relief when I still got groups. Moreover it was a relief when I was a good group healer.
From the point of view of a tank, paladins are great, until the crap hits the fan. I have had many wipes because the paladin tried to keep another member of the group alive against AoE damage and didn't get back to healing me in time. I've also had a number of wipes because the paladin's use of down-ranked heals - they were healing to stay on full mana, not keep me on full health, d'oh.
The utility of a paladin healer isn't great. Sure they can heal until the cows come home, and then some, but only in a serious, going-to-keep-you-alive kind of way on a single target. Once you start having them heal multiple targets they have to up-rank their heals and they no longer fulfill on of their major selling points.
Of course, the paladin's real advantage is her bubble. When she pulls the heat off of you, all she has to do is pop her bubble and it will come waltzing right back like some kind of forgetful puppy, with really large teeth.
I like paladin healers, don't get me wrong about that. But I accept they have their limits and that I have to work that little bit harder to make sure they're only healing me.
Shaman fall into two very extreme categories: those who suck harder than a suped-up turbo Dyson, and those who heal like gods.
The defining point separating the two extremes is how they use their abilities. The worst tend not to make full use of all of their powers, don't pop down totems, don't use Earth Shield (indeed, may not have Earth Shield), etc.
I really like being healed by a shaman with skill and understanding of his class. The other shamans can go take the long walk.
Sadly, the good shamans are few and far between and if you find one, friend him.
I have a problem with druids. Their abilities seem to be focused on healing tomorrow, rather than healing today. They've a wealth of heal over time abilities, some really strong ones and some fiddly to use ones. But they seem to lack the very thing that makes a paladin great - solid chunks of healing in response to damage taken.
Druid healers seem to have to predict when I'll be in the greatest need for a heal and then place healing on me to fill that need ahead of me taking the damage, which is a precarious position to be in. To be blunt, I don't trust druid healers.
I've had some really bad experiences with restoration druids, and a couple of nice ones. On the whole I'd take a restoration druid, but I'd be thinking about a holy priest.
In conclusion, I'd rank the healers in this order:
- Holy Priest
- Great Resto Shaman
- Holy Paladin
- Resto Shaman
- Resto Druid
You may well disagree with me on that ordering, but such is life. Everyone has their opinions.