I started playing in Cata, so MoP announcement was the first time I watched blizzcon. I should have been a bit more clear that from MoP and onwards things seemed a lot more fleshed out. Also, I do not think that scenarios were a significant addition to the game in MoP, to the point where it needed a lot of emphasis on, or fleshing it out early, considering how little they did with the system. Regarding challenge mode, yes, they were awesome, but it's was hardly the central part of the expansion.
Here we had soulbinds, soul conduits, and literally everything that had to do with covenants aside from their cosmetics being completely absent from the presentation aside from a small UI of a soulbind. The single biggest core of the system, same with torghast, which ended up being such a watered down concept compared to what it seemed like potentially, and last but not least, literally 0 clue on what to do with classes other than bring a few things back.
So much for Holinka's post before blizzcon saying 'I am especially proud of the work the class design team has done, can't wait to show you on blizzcon', and then we got mostly stupid shit back that is so situational that yes, it will feel good that you will use it once in a blue moon, but the immediate gameplay was completely unaffected, and had it not been for the amazing testers, blizzard would have no clue on how to make some classes better...
Still hyped for shadowlands, but saying that the game got a lot of dev time, when I play it daily with friends to test m+, and to this day, there are entire dungeons (theater of pain), which as of the most recent build, has like 90% of its mobs constantly evading, and the beta having soulbind trees breaking and not working, not letting us test them for a month or two now, when the game is 1.5 months away from release, is absolutely ridiculous.