There were a lot of balancing changes in general that went under the radar.
AoE changes in 2.2
Melee haste nerf in 2.2
Expertise introduction in 2.3
as examples…then of course countless bugs that had to rectified.
By Patch 2.3 Blizzard had also balanced the classes as they wanted, and by 2.4.3 it was fine tuned.
It would make sense to release 2.4.3 and then gate content, professions, and badge gear by phases.
But it’s Blizzard so who knows!