The voDleH is only 412 meters (according to KA) and that's smaller than the Excelsior class (also considered a BC), which is 467 meters. I'd say the voDleH is just the right size for it's purposes. By Klingon standards, it wouldn't be big enough for a DN since the Accuser is 610 meters, 200 more than this beasty. Of course, the ridgeheads always did have an inferiority complex in regard to their capital ships.