My hated of a particular class changed with each expansion. Here's my list and my thoughts on it
Vanilla - Warrior (Why do I keep dying!? ><). Favorite was Mage, second was Priest
Burning Crusade - Rogue (Stabbing things wasn't working for me) Favorite was Mage, second was Paladin
Wrath of the Lich King - Shaman (Always forget totems). Favorite was Paladin, second was Warrior
Cataclysm - Warrior (byebye armor penetration ;_;). Favorite was Paladin, second was Rogue
Mists - Mage (can't stand my own mage anymore ;_;) Favorite was Paladin, second was Hunter
I also was never a fan of Death Knights, but I leave them out of my list since I never levelled one past 74, despite trying to do so, repeatedly.