When all else fails RTFM (and a Campy secret handshake)
I took my main bike for a longer ride yesterday, a flat 35 miles along Rockaway Beach in NYC. Through the whole ride though I kept thinking the shifting still wasn't right on my Chorus 10 setup, and I had just taken off the cassette, cleaned it, and gone through the Park Tool method to adjust the derailleur. Last time I did it it worked beautifully. This time though I spent every ride so far trying to tweak it but couldn't get it right. Then it dawned on my, what if the spacers that I thought were all the same, weren't? So I pull up the Campy manual online, take off the cassette, and sure enough I swapped two identical looking spacers that were different thicknesses. Luckily the spacers are stamped with their thickness. I put it back together, correctly this time, and now it shifts like brand new after a few quarter turns of the adjuster.