why is priest a no-no?

[Ualaa]

If your team does not include a shaman, then a resto shaman is a very strong contender for top healer.
They have Earth Shield and Healing Stream Totem for some passive healing.
They have Lesser Healing Wave (fast) and Healing Wave (big) heals.
And Riptide is instant.
Chain Heal, is one of the better AoE heals in the game, but has a casting time.
They're better if you anticipate, rather then react to damage.

Totems can be huge for a team, especially casters.
Bloodlust/Heroism is a very strong selling point.



I personally prefer discipline priests (with some holy) as my healer of choice.
They are mobile, put out more dps then any other healer spec, and effective at single/aoe heals.
Plus they have so many options to mitigate damage.



Druid healers are also mobile, they have massive survivability and some nice toys.
I don't like them as much as the priest, but there's certainly nothing wrong with druid healers as far as boxing goes.



Paladins can work, if you want to use one.
A shield and armor, makes for a very durable healer.

They're lacking on AoE heals and healing while moving.
So that's two major marks against using them as a boxer.

[Ughmahedhurtz]

For PVE, just about anything works. Just figure out what utility you want in your group the most.

Better AoE heals? Priest, then Druid/shaman
Better single-target heals? Druid/Pally/Priest/Shaman
Want curse removal ability but no disease? Druid
Want debuff dispels except for curses? Pally
Want passive cure poison/disease? Shaman
Want anti-fear/sleep + passive AoE heals + passive AoE damage? Shaman
Want +DMG for caster DPS? Shaman
Want in-combat rez? Druid
Want wipe prevention? Shaman
Want usable healer threat reduction? Pally/Shaman
etc.

Pick what you want and go with it. With the way gearing is in WotLK, any of them do well.