A skilled healer is always better no matter class tbh!

Ive played with a paladin and the main problem is that mass dispell + purge pwns you hard, the paladin was realy bad however so this vary. It should be pretty easy vs teams without offensive dispellers, they are rare however.

Priests feels better for me atm with PW:shield and lots of buffs + aoe fear wich should be used right. I never played with a decent paladin imafraid and they seem to be rather rare!

Misery contains lots of multiboxers so most knows how to counter you effective.

Dalaran sewers is a realy good arena if you turn the positioning into your favour and orgrimmar arena is superb since most teams dont have a clue how to position themselfs. Ive seen one team using orgrimmar to the fullest and im extremley suprised how good the pillars/fire can be taken advantage off.