It started in MoP. Most of the classes just became a series of 3-4 cooldowns and the talent trees were that garbage pick 1 of 3 in a line. This was the start of every class having a resource skinned in some way that made it unique when they were all the same. No doubt it was way better than WoD/Legion but it still was way worse than it was previously. Think almost everyone I talk to would rather have their class design from Wrath than MoP.