Lore-wise, I could maybe see a portal room being in ‘the demilitarized zone’ at the gate so that if an invasion came THROUGH the portals it wouldn’t be in the middle of Orgrimmar… but such an idea is ridiculous because our mages would swallow their felcide (like cyanide but more evil-green) pills before they help Allies. 
I will say that it’s less disorienting getting from the new portal room to the cataclysm portal ring. Out, turn right, go up. Before it was… um this tunnel, or that tunnel, up and spin around… okay there’s the zeppelin towers, must be that way, oops wrong tower, over that way then, got it.
Slightly longer path, but much clearer. I can live with that. Still no reason to remove old portals from New Dalaran.