Asking for opinions on a Tiffany dial is like asking if people believe in extraterrestrial life. There is nothing tangible or concrete to base an opinion on. The legitimate signatures were added afterwards, in different fonts, with different ink, often skewed or off-center. Which also makes them a prime target for counterfeiters.
As a skeptic, the only Tiffany dial I trust is the one that comes with the original purchase receipt. It blows me away that people are willing to pay such high prices for undocumented Tiffany-signed Rolexes. But these days, if something is sold at one of the major auction houses, many buyers take that as proof of authenticity.