Since the devs claim Divine Vengeance is ddo version of pnp paladins holy avenger which most likely a longsword version of the iconic Carsomyr (a two-handed holy avenger). Since level 20 this weapon is out shined by other longswords at lvl 20 and you can only get it's full potential by being a lvl 20 paladin. In pnp also there is and epic version of a Holy Avenger which is a Holy Devastator so why not implement it here also. Upgrading the Divine Vengeace into a better epic version by doing certain quest or collecting special materials to craft it.