Battle for Azeroth attempted to tell three storylines and ultimately in my opinion failed miserably at all three.
However I think it could have been done…if they did everything backwards. Have N’zoth break free following the sword of Sargeras being plunged Into Azeroth. Have him influence the factions to mine Azerite and march to war. Then the factions delve into aszhara and mechagon seeking answers to stop n’zoth or find a way to win the war. Finally we would end with each faction landing at the zandalari and kul’tiran stuff. I think it would deliver a much smoother transition from legion and would be a more compelling narrative.
TDLR: Switch the patches of BFA around, with n’zoth first and battle for dazaralor last.
Well… but you forget that having a faction war addon was the main premise, and maneuvering Sylvanas to the position where she would abandon the Horde and lead in the Shadowlands addon was what they already had in mind.
Apart from that… It’s hard to propose a change that would have made BfA’s story significantly worse, so I wouldn’t feel surprised if your direction would indeed have felt besser.
Bwonsamedi’s appearance at the end of this would be scenario would perhaps be a better tie in to Shadowlands I feel. Particularly with Vol’jins soul and his “boss”.
Because seemingly “Battle for Azeroths” only intention as an expansion was to clean up the mess which was still around on Azeroth. Faction conflict, Kul Tiras and Zandalar, Aszhara, N’zoth. These things have been resolved…at least in Blizzards eyes (let’s not talk about the fact how BfA actually resulted in giving the Alliance so many reasons to outright annihilate the Horde that only the atomic bombing of Thunderbluff with all civilians still inside would be enough to put both factions on even moral ground ever again).
And Shadowlands will now deal with the Scourge, the Lich King and Sylvanas (finally I might add. I grow tired of her). So we have finally wrapped up Warcrafts story.
You cannot really fix a story, which is fundamentally broken like BfAs.