I tried to the WE Grand Campaign a few times but they're just too frustrating to play given how they can't build real settlements.
So when I booted up a new VH Empire campaign, I assumed the WE would get wiped out pretty fast or at least wouldn't be able to expand effectively.
Boy was I wrong!
I ran the VH Empire campaign twice and the WE managed to overrun all of Bretonnia, Estalia, Tilea, and everything north of Altdorf.
They never declared war on me, and never allied with any faction other than that one dwarf clan.
I took them on in both runs and it was a slaughter, the only thing that slowed me down was how long it took to rebuild the settlements the WE had taken, rather razed, since nothing was left to build on.
Then I marched into Athel Loren and razed the 4 settlements (or rather 3 as the Beastmen had already burned King's Glade and the Oak of Ages). It was quite easy actually.
So I don't get it why are the WE so damn powerful? Does it have something to do with the quirks of the AI mechanics?