I have a rottie with a beautiful tail and she has no problem with her tail during her schutzhund training!! Was your dog a working dog???
I walk with a friend who has a an imported rottie from New Zealand with a docked tail. He has had a nightmare time having a young Rottie with a docked tail. We get abused when walking them together, no vet will treat the dog and the RSPCA have been called by many people and visited him. He would never buy a dog from New Zealand again.