Austen isn't from the Victorian era. I think it's the Regency era.
Yes, Middlemarch does require a certain knowledge of Victorian politics, particularly regarding reform. I would call it a novel of manners because you need some understanding of the workings of nineteenth century society (both early and late) in order to appreciate. Dickens is a characaturist/melodramatist, so his novels are understandable on a simple level if not a deeper one. Even though Hard Times is about utilitarianism, it has the more universal message of the dangers of destroying fantasy and imagination and turning people into machines. I think that Eliot's prose is slightly dryer and not as biting as Dickens, but then, Dickens can be dry at times as well. It's that typical Victorian style.

