Anyway, here's what I tried:
I have a 'chroma>smooth-then-sharpen' filter, which, again, returns to blockie after it's rendered in the Final Cut timeline.
However, if I apply the filter, don't render, and instead export as 'uncompressed 10-bit 4:2:2', then put that clip through my mpeg2 encoder, I get this:
Not perfect, but much less blockie reds. The color change is from some desaturation I applied.
I guess this method bypasses Apple's DV codec ... I don't know ...
Is that silly to export as 4:2:2 uncompressed?