But it doesn't matter if it's easier or not.
The end result is whether the game actually gets more balanced or not. And what we see is that time and time again, Blizzard self-contains the class design and balance of all specs within the confines of each expansion, and treats them all separately from one another. They clear the slate and start new every time. The result is a balance that never gets better and better, it's just different each time.
Even if they take out the needless complexity of Survival that existed in TBC, they're still adding the complexity of Covenants and Artifact Weapons and GCD changes today. The game doesn't actually get more balanced as we move forward. It just gets differently balanced.
Whether they add a new class or not, they're going to run into blunders, period. There has never been an instance of WoW that hasn't been blundered through, right? So why are you making an argument that it's easier with less new stuff, when there has been no case where it actually HAS been easier with less stuff? Each expansion ALWAYS adds new features. Every. Single. One. And my point is even if they aren't going to add a new class with 3 more specs, they will always add something else that will effectively require the game to be rebalanced regardless. There has never been an expansion that ONLY focuses on balancing with no new systems or changes to the system. Each iteration of WoW has had some form of major change or addition.
Again, WoW is not a balance-oriented game. It is a progression-oriented one.
Wrong, because it hasn't been Bobby Kotick's mandate to have WoW be designed in the way it has been.This might change with the departure of the garbage human known as Bobby Kottick and Microsoft allowing more freedom and not being so penny pinching like Activision Blizzard has inflicted upon the developers more and more over time.
It has been the WoW Dev's own choice of taking this direction and carrying it through this long. And frankly, that is WoW's strength over the competition, so it would be difficult for them to suddenly make the shift to anything else that they aren't known for doing well.
WoW didn't suddenly have this type of game design philosophy after the merger in Wrath. This has ALWAYS been how WoW approaches balance and design. Even in Vanilla, they were even more ass-backwards with rolling out patches focused on a single class each time, do you remember that? You'd have to wait months to get your turn, and only if your class was lucky enough to get addressed. They never really intend all classes to be fully balanced against one another. Their goal is to provide enough balance that everything falls within (using BS numbers) within 10% of the top DPS, and they'll tweak the numbers to fit things accordingly. And honestly it doesn't really matter if certain class gameplay feels good or feels bad. They'll easily cut things, replace things, remove things at will.
Metamorphosis was one of the best Warlock specs ever designed. It performed well, it had very engaging mechanics, and it was a rotation that had a lot of risk-reward skill involved in maintaining the demon form as much as possible in a Raid environment that forces you to reposition all the time. And they easily removed this from the Warlock to give them the Summoner gameplay, which took over 2 expansions to get right, and still pales in comparison to the Metamorphosis gameplay overall. Or I could point out how Enhancement Shaman pretty much gets the shit-end of the stick most of the time, in almost every expansion. They're only really good in PVP, while their performance in Raids has them being fairly mediocre and bottom of the barrel most of the time, with a handful of times seeing them edge up above-average. Blizzard isn't looking to fully balance this spec to compare to all others. They're just happy with it being viable.
That is the state of balance in the game. We aren't going to see class design and mechanics get better and better over time because that is never really their goal. Microsoft taking over doesn't change this. At all.