The Venator's carrier role and defensive guns

Is the Venator a good example of a battle carrier?

No; it is fundamentally a carrier with unusually heavy defensive guns, and its fleet value still depends on using aviation as the primary mission.

The Venator's principal role is to carry aircraft, with substantial guns added for its own protection. Space permits attack from more directions than a surface carrier can readily cover with its aircraft. That makes an armed carrier a reasonable design without establishing an equal battleship role. Its screen depictions and supporting reference material also give very different impressions of the number of craft aboard.