I’m a fairly typical American and one wife is plenty. I don’t think Barsini is meant to be typical of any culture, but rather a brilliant artist who breaks social conventions. I believe that he is loosely based on Pablo Picasso. I doubt that Picasso actually had wife, ex-wife and mistress all under the same roof, but he was allegedly a notorious womanizer.
I was never a big fan of this episode either. However, after reading this forum and reading how many people loved it, I saw it through different eyes and found a different appreciation for it. Try to disregard logic and the standard “Columbo” formula and instead enjoy the “dream element”.