We have invented three types of hero and four types of wizard for convenience and to provide comparability between adversaries, but this does not mean there are no individuals whose abilities vary wildly from the values we have given for Champions, Heroes, Lords and Wizards. There are of course more than you can imagine!
Although we are not concerned with the rules for special characters here it is worth bearing in mind that they can be incorporated into your battles if you wish. For example there are the mighty leaders of nations such as the King of Bretonnia, the Emperor of the Empire, Orc Warlords, the Witch King of the Dark Elves, and many more. There are also important military leaders and high ranking nobles, such as Bretonnian Dukes and Elector Counts from the Empire. All of these special characters are individual and quite different, and so are represented by their unique characteristics. Some are therefore better fighters than others, but some are better leaders, while many carry specific magical weapons or ride large monsters.
The details and extra rules for special characters are not given here in the Warhammer game - there are simply too many and space does not permit it. Details of heroic individuals will be published in Warhammer supplements and White Dwarf magazine as appropriate.