So, if this thread interests you, chances are you like playing IMBA classes (imbalanced) that happen to appear after a new patch or expansion. After doing a little bit of thinking, its quite easy to figure out which classes you can play to give you the unfair advantage you need to win.
Any class that have these traits in a patch or expansion will be that much closer to imbalanced or overpowered.
-Reduction in cool-downs
-New/More CC spells (these usually only happen in new expansions)
-"Reworked" Abilities, usually when an ability is reworked often times what was lost from reworking it is added in as a passive of some sort.
-Healing increase (whether it be a formula change or straight number tweaking)
Traits that really don't imply a class becoming FotM or becoming nerfed or buffed
-Anything that deals with damage of something really doesn't imply something become buffed or nerfed (I can already sense this one becoming arguable, Warriors Tfb was a mechanic, not a straight damage increase, examples would be like Paladin: Hammer of Wrath damage increased by 5%, it really doesn't make any difference in the end because of the sheer amount of self healing and how resilience works)
So in TLDR, if your class is getting more mobility/cc/healing, or getting less downtime, chances are its getting buffed. And keep an eye out on these classes because they'll become the next over represented class in which you can abuse to get the unfair advantage. Warrior representation from end of Cata to beginning of Mists? Sky rocketed. Cause they got reduced cooldowns, more mobility, more CC, and an increase in their self healing that requires no upkeep. Which class do you think will be next? Who will flock to the next entity of the game to have an easier time getting to the top?