MoP is often looked back upon fondly.... and I personally really enjoyed Legion a bunch... I'd even say SOME of WoD had some very nice qualities with how the gearing system worked back then (getting up to 3pc each week from arenas, (tr)Ashran, and winning the highmaul coliseum 15-25player FFA event)...
But yeah, your point is correct, in every single expansion there's been something that was terribly balanced, often at the start of the expansion.