Try a pigg viewer, a lot of message text for the UI menus and dialog for localization is in the .pigg files. Not sure about all of the NPC chatter but I can't imagine them downloading that text on-the-fly at runtime.
misc.pigg has a lot of text like the above, for example.
Rule #1 of MMO network code is: Don't send it if you can install it on the client.
It's not inviolable, but to deviate would mean there is a big benefit to counter the disadvantage of further burdening the server with Stuff It Shouldn't Have To Do while still coping with all the Stuff It Has To Do. An advantage like dynamic branching decision making and associated text that they only update in the server without needing you to patch anything, at the expense of having to download it lazily at login, map load or whatever event makes the most sense for locality, prediction and perf.