This might work for you:
[Media Type]=[Audio] -[Genre]=[],[Soundtrack] [Mix Album]=0 ~limit=-1,1,[artist],[genre] ~dup=[Album Artist /(auto/)] ~a
It does the following:
1. Exclude all files where Genre is either empty or "Soundtrack"
2. Exclude all compilations, or "mix albums"
3. List 1 example of every artist-genre combination that exists in the library.
4. Keep all duplicates of artists, discard the rest.
5. Expand to full albums.
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If you use that in "Step 4 - Files to show" and add panes to suit your needs it should all work fine.
If you distinguish soundtrack albums in some other way than Genre, you'll need to amend the search to take care of that.
This should leave you with artists with multiple genres. You will be given one example of each, and the assumption is made that you will know which of them is correct and which of them need changing.
-marko
Good enough?