Okay but Silithus is actually in a reasonable proximity to Khaz Algar. Undermine isn't. The Kazan loading screen puts it directly north of Pandaria.
So far nothing's controverted my immediate theory that if the additional TWW zones are further down, we're going to hit the tip of the Sargeras' sword by the end of the expansion. That seems like the whole point of this expansion. The sword is going south - southwest & if we go deeper north - northwest the points meet.