We have collectively searched for and pointed out various shortcomings in this portrait and Mr. Buss is not even here to defend or explain himself and his work. It has been an entertaining thread to follow.
I have tried to imagine Mr. Dickens reduced in size to match his desk or the desk enlarged to match Mr. Dickens and wonder if the size difference might have been intentional. There is a lot going on in this picture and a slightly larger Dickens catches the eye foremost before view moves to the characters, furniture, and room surrounding him. If he was smaller or everything else larger I wonder if he wouldn't be lost in the commotion.
So, I am going to agree with Walrus. There is nothing wrong here.
Okay, Nuuska, you have our assembled answers. We await yours!