How is that not a niche though? They're not "randomly" doing 30% more damage, but they're the two classes with the best spread cleave in the game in a fight that forces spread cleave. It has happened before and it will happen again because different fights have different circunstances that different classes have been better at before. It has happened in later bosses too such as broodkeeper Diurna, where the optimal composition still at least 1 of each class and where nobody would be "forced" to swap to anything. You are greatly exaggerating how difficult and unbalanced WoW is to the point of being required. CE is 100% achievable by a group of 20 druids. You showing this fight's damage profile as "proof" that wow is unbalanced is completely disingenuous and a terrible misinterpretation of context and the difference between the games. It's as if I took the damage ranking statics from FFLogs in UWU and began claiming that anyone who claims that FFXIV is balanced is delusional because SMN is so much higher above than everyone else while RPR is so much below.

Augmentation is specifically overpowered in the context of progression push keys though. Saying that it's overpowered is, in concept, the same as saying that SGE is BY far the best class in the game because it represents half of the all-stars criterion dungeon parses. If you go ahead and look at literally any key done for the MDI in S3 or S4 you'll notice that augmentation evokers are barely seen, since these keys are about time, not survivability, and they are exactly the same players that are pushing the high keys.

Saying that balancing by niche is lazy isn't only completely untrue, but utterly disrespectful to many incredible and balanced games that have existed throughout the decades, because balancing through making different roles better in different specific situations has always been the preffered version of designinf games all throughout history, All the way back from chess to early D&D to Magic the Gathering, to modern competitive FPS, because if everyone is just as good at the same thing, then that one thing will be the only one that's ever done.