I used to hate Priest more than anything and only leveled one just to say I had it at max level.
After playing one in TWW, I’ve softened my stance and have moved the Priest from last place to just ahead of the Mage. Not saying I don’t like the mage, but I’d play Shadow over any of the available Magi specs.
Now if I had to pick a class that I absolutely refuse to main, that would be the Evoker. It’s not a bad class, or one that I dislike playing, but I would hate to have it as my main. I would probably quit this game if that were my only option.
Evoker is a class I jump on to play around when I want to try something different, but Devastation is not a spec I would enjoy playing all the time. I know it sounds weird not having it as my last place class, but I do enjoy it more than playing Frost, Fire and Arcane. Just not as a, “this my main character” class.