Personally, no. I happen to enjoy Dicken's characterizations, and while there are one or two characters that may be considered stereotypes, overall Dickens achieves well rounded characters. Take Sydney Carton, for example. Though we are introduced to him first as an alcoholic, he becomes a selfless hero, with his decision to take Darnay's place at the guillotine. Sydney becomes almost a Christ like figure at the end, however, with his earlier sins, and alcoholism, we cannot see him solely in this way. Therefore, Carton is not an extreme or a paradox, but a flawed figure who does something magnificent. You could also consider Charles Darnay to counter the argument of the exaggerated characters in Dickens novels. Darnay is a passive character, and although both of his arrests are from his trying to help people, he is not exaggerated, in fact, he is unable to accomplish the heroic things which he sets out to do.
To be certain there are characters in Dickens that have been exaggerated, however the characters remain rounded and real in the mind of the reader.