Getting different amounts of change though doesn't have to mean that one is traceable.

Picture the same set of inputs, but a set of outputs all denominated in 30BTC, 10BTC, 3BTC, 0.1BTC, O.03BTC, etc.  Up to whatever set of denominations you can make at least ten each of and down to whatever denomination people are willing to give up as a mixer fee to enhance their anonymity.

Now some participants get more of one denomination, some participants get more of a different denomination, but with ten of each denomination there will always be a way to split up whatever amounts among three participants, and there's no way for an eavesdropper or block chain snoop to know which is whose.  They can't even use the number of each denomination issued as a guide to what particular amounts were paid out.