Mabbu has a decent size guild also. There will be TONS of smaller DZ guilds - more than usual. But for the largest guild to be DZ only is a change.
To my knowledge, both servers Vicious has ran an OW guild on there have been DZ guilds larger than his OW guild at least in the start. Coirnav there were DZ guilds larger and Mangler there were a ton of DZ guilds larger until RI folded in kunark and then reformed as Bloodthirst merging a bunch of DZ guilds together making them the largest guild.