Lo Kerm,
Quick breakdown between the priest classes:
'clerics' have reactive heals, pool of X mana available to auto heal when damaged for Y minutes
'Druids' have Regen heals, constant X heal over Y time
'Shamen' use Wards, X hits buff for Y time.
All have solo & group verison of these skills, they also all have direct heal spells.
In small group 'clerics' have the easiest time, cast the reactive and sit back, the odd direct heal if the mobs does a special.
In big groups is best to have 2 diff types of priests rather than the same.
cleric/shamn Druid/shaman i think are the best,
From experience im usually grp'd with a Cleric, so ive time to go make a cuppa during kills !
I'm playing a Warden and a monk atm, enjoying both.
Om