How? You're comparing an entire expansion to one two level zone? Be realistic.
Also, you're assuming that I want an entirely underwater expansion. Which I do not. 2 underwater zones and an underwater dungeon + Raid would satisfy me entirely. You're stating opinions as facts for the majority of your post, so I'm not bothered replying to those.
Completely forgetting about their old work? Are you telling me that due to Northrend being in the snow, and there only being one other snow zone in the game IE winterspring, they had to entirely rework their designs on every model they've ever made? Or maybe most of them would just need to wear snow suites or something and then look identical? If you'd even tried Vashj'ir you'd know we don't have to wear scuba helms. Sorry, but I'm just using your own logic here.
Not trying to be insulting, but your post shows a complete lack of imagination. People said all the things you're saying now about Pandaria. There was no lore on Mogu before Pandaria ,& their story with Lei-Shen and The Isle of Thunder was epic and I see it regarded as one of the better raids WoW's ever had quite regularly.
Side stories? What about Mak'aru? What about the uniting of the troll tribes and Vol'jin? Jaina & Kul Tiras? Tel'abim? Lets not forget about the potential we have with Neptulon taking control of the Krakens? Maybe Sylvanus becomming leader of the Vry'kul/Kvaldir, and all of that is without even considering the Naga & Aszhara & old gold lore they'd be taking on to building up void lords with. There is so much potential with a Naga focused expansion, as there is with every other idea.
& would ya look at that, I didn't even mention the Murlocs.
One or two zones... yes!
An entire expansion... no!