Well, DC being the solo artist is the ultimate bottleneck for more than a year now. He's doing nothing but drawing and all the stuff his team codes, poses, writes, animates etc. doesn't influence the time the game as a whole needs to be made. So I don't really see how there can be gains in efficiency when it comes to the total amount of content at this very moment, now that the route is clear. So reworks aren't bad at all, what's bad are reworks which require old art to be removed and that shouldn't happen with any "new story" i.e. Roxxy, Diane, Jenny, and everybody who is to come. Edit: If it does happen I'd agree and they made a big mistake in the process, but I seriously doubt it will.
That said, I'd say one has to exclude the first year when it wasn't clear what the game was to become. They now have to correct the mistakes and decisions they made back then. So yes, the art which was made before they switched to the rig-system etc. (basically before 0.15) is to a degree lost, which is highly inefficient. But DC started making SS to teach himself working with renpy/coding, so one can hardly blame him for not having the vision, that he'd hire 5 people and produce a game which would last 4 years or more.
