I generally think BfA is an all-around decent expansion. It has its ups and downs, like any expansion, but I don’t think any shortcomings shine through to the degree that it reveals something about the development or production side of it.
Blizzard does have overlapping “teams”.
They have one team that’s dedicated to work on content patches, so that’s how they manage to go from one patch release and straight into the PTR for the next one.
Beyond that, the actual design of the game is fairly consistent throughout the patches. I think the only design overhauls Blizzard have done in BfA has been in regards to the Azerite Armor and the Titanforging/Corruption system. That’s actually an unprecedented small amount of re-design during a current expansion. I mean, Blizzard will usually revamp at least a class spec or two.
So from a sheer development and production point of view, I think BfA has probably been a very smooth project. It’s really only the Azerite Armor system that has been a noticeable bump in the road, I think.