Well, in every scene and mission of WC3 where the Dreadnaught appears, it is a lot smaller than 22KM, perhaps even smaller than 2.2km.
The last thing that actually annoys me in WCU is this typo that became fact. 22km is really not reasonable... and it gets less reasonable if you consider the mass of the ship, even if you try to justify that by saying it's kinda "empty". The number of turrets is also pathetic for sucha long ship. It's like you can park several Confederation CVS between each pair of turrets...
However illogical the 22km figure may be, it's become official, and neither you people will admit nor I will. So, let's live our lives and try to be friends.