That is exactly what mixing should focus on.

I can take 73.26 and split it myself in to smaller sizes in a way that looks like a series of purchases on my own node with no cooperation needed from anyone else. What I can't do is anonymously combine all my dust addresses into an address large enough to be useful without outside assistance. A client can be very careful to use different incoming addresses for every receipt and to never link addresses but at some point the user is going to want to spend an amount larger than the balance of any single address. The only way to avoid this situation without compromizing anonyminity is to have the ability to securely combine small addresses into larger ones.

That's why I think mixing should be focused on transactions which have many more inputs than outputs. https://bitcointalk.org/index.php?topic=93390.msg1036811