Unfortunately these kinds of activities do not help much to restore the population balance. Servers like Mal'Ganis, Sargeras, etc, are basically PVE servers for their respective dominant faction. Other than going to CRZ lands, there is absolutely no WPVP, and I guess some people like that way.
I don't know why Blizzard remains hell-bent on refusing server mergers for US realms. On TW side, we just had mergers for six of the biggest lopsided servers, and the result has been great.