The Pokeradar didn't raise your chance for finding a shiny. It rose the encounter rate up, you were guaranteed a battle so long as you stepped into the patch of grass. You still had the 1/8000 chance that that Pokemon would be shiny.
This is the same if you use just the Old Rod to hunt for Shiny Magikarp or the same as using Sweetscent in the grass/Cave. If you raise the encounter rate you have a small margin to find a shiny faster than normal. It doesn't lower the 1 in 8000 chance of finding a shiny.
I know thine because I've gotten more shinys breeding than I have with the Pokeradar.
EDIT: I think it was useless and never got anything worth merit from it, but I wouldn't mind seeing it reappear. Guaranteed battles are better than random encounter.