>What is an observer?
There are two issues when it comes to consciousness: the experience and the experiencer. If we conceive of these two concepts as ultimately one in the same problem, then there is no issue with focusing on kinds of processing rather than observers as its ultimately addressing the same issue from a different angle.
If you conceive of these two concepts as separate issues, then your target should be the experience rather than the experiencer. If you consider all the features that make up an experiencer (sans qualitative experience), then these features can be cashed out in terms of information processing. The mystery isn't here, but in the qualitative experience.
>Most of our insights into how human mind works actually describe how a philosophic zombie will work.
Only as far as our descriptions of a brain are "local" in the sense that they don't consider global properties of such an information processing system. That is, we can have a description of a system that makes accurate predictions without making any high level statements about its processing. We can conceivably describe the workings of a biological creature without ever (explicitly) mentioning molecules, proteins, cells, DNA, action potentials, etc. Yet if we concluded from this that biological zombies were conceivable (physical systems that behaved exactly like biological organisms just without cells, proteins, etc), we'd be mistaken. But this is the same kind of leap that we make when take the p-zombie argument seriously.