The last time classes were pretty balanced across the board was MoP.
As it stands currently there’s only 1 choice in talent rows for certain classes. Like Affliction taking Haunt 100% of the time.
You kidding lulz? I was blessed to be a warlock main in MoP and you tell me shit was balanced? I literally creamed everyone DPS-wise by a good 20% margin in raids almost on every boss bar one, not because of skill, but because it was so blatantly OP by the last tier, which lasted more than a year of faceroll.
MoP was a great expansion, but balanced? lol no.
I've always been a firm believer that classes should excell in different types of damage, healing and tanking. But it seems to be unpopular because people are so obsessed with those ridiculous charts.
I find raiding normal or heroic are the only places I'm allowed to actually have fun without some fucker watching my every move being all anal about having the "right" spec and/or gear setup.
Raiding mythic just feels like some number simulation game, sure progression is fun but tedious at the same time.
You've played since Cataclysm as you've stated in your post, so let me just remind you that class imbalance has been a thing since well.. The game first started. It's impossible to achieve class balance without classes becoming homogenized and shoe-horned into having similar designed abilities and spells. That's the drawback of making each class differentiate from the others, imbalance will happen.