I think Dollhouse was too messy a concept to sustain over several seasons. The filler episodes just never worked for me, while the mythology type episodes have always been fantastic. Most shows need both to work in the long term I think or they have to become completely serialized like Lost. It doesn’t look like Whedon had enough story to do that so I think it is almost better that the show was cancelled and Whedon can go our in a blaze of glory.