Thanks, Finninbas! I don’t remember seeing this article back in the day. Some quotes for the record are below.
I used to like him for that until I found out that BfA is likely the price we paid for it. 
Okay, some quotes below from the Forbes interview of January 30, 2018, with Alex Afrasiabi and Ion Hazzikostas. (“Newman” is the interviewer, Heather Newman.)
Newman: Talk a bit about the decision from a story perspective, the world perspective. I think everyone was curious as to what happened to Jaina Proudmoore. I’m not sure as many people were curious about what happened to the former Horde Warchief Thrall, especially since he kinda said, aw, my hammer isn’t talking to me anymore, and then wandered off. I think everyone thought that was (former senior vice president) Chris Metzen’s goodbye when he retired.
Afrasiabi: Oh, no, he’s coming back. Metzen’s coming back. Better believe it. That’s why Thrall’s back. [He laughs.]
Newman: Lead me through that thought process for the new expansion.
Afrasiabi: We consider the faction divide foundational to Warcraft since [its real-time strategy] times. As we kind of look at the equity we have in certain fiction, this is the one that’s at the top of the list. We’ve danced around it for so many expansions now that we feel like it’s time to pay it off.
Now, there’s some of the story that you haven’t seen yet, of course. Actually there’s quite a lot of the story you haven’t seen yet. Over the next months, more of that will come to light.
As we’re talking about things like enemies, we’ve fought everything. We’ve fought everything under the sun and then some. We’ve gone to other planets, other universes, you name it.
Newman: Back in time!
Afrasiabi: Back in time. It’s interesting. I think about this a lot, because I’m a nerd. Especially in Warcraft , do we become what we kill? And we’ve got these characters in the game, these Alliance and Horde players, who have done it all, and in killing an old god, do we take some of that with us? In killing an elemental lord, do we take some of that with us? A dragon aspect. A titan. I think we do.
And so we’ve set the stage for, when we say, what is the most badass thing out there? I would argue it’s the living god that put an axe in the side of a titan, more so than the titan itself. So when I look at a player character and I say, look, we have a world populated with living gods at this point, that have ideological differences that cannot be righted, what happens in that world? Well, this happens.
I’ve got this group of gods and this group of gods that will never get over their differences between the humans and the Forsaken, the orcs and humans. Never. The Night Elves and the trolls. The Night Elves and the Tauren. I mean, there’s so many different racial divides that have melted away into the background, but they’re still there. For those races, those things are still there.
How much land have the Night Elves taken from the Tauren, from the trolls? These are the things we want to settle, and that’s what I think this expansion is about. Now, of course we’ll see other things come into the foreground as we adventure through this, because certainly there are forces in this universe that want the outcome of this. So we’ll see. That’s the TL;DR version.
Hazzikostas: On the story side, I think it actually is that faction focus, front and center. I think in many ways, what classes were to Legion, factions will be to Battle for Azeroth. Instead of the class campaign you’ll have a war campaign. You’ll be having this feeling of working on behalf of your faction to further your efforts in this battle that consumes the whole world. That’s exciting.