Disclaimer for me, I am not a breeder and I am still learning about all of these things myself. So my opinions on this are purely as a layman who might someday be purchasing a puppy from a reputable breeder. I also go for working lines. A CH in front of a dog's name is not enough to interest me in a particular breeder, especially if there's no working titles on the dog. And no Kimbertal lines. That kennel is not a responsible breeder and there is no way I would pay 4K for a pup whose only redeeming factor (ha) is a Kimbertal champion several generations back.
I know linebreeding and inbreeding can sometimes be done to fix traits you want in a pup. I also know that doing those things too much can cause all sorts of health problems and that a lot of breeders purposely avoid breeding close relatives- for good reason. If I were buying a pup, I would not want lines that had the same ancestors used in both the dam and the sire. I wouldn't want inbreeding at all unless it was extremely limited and not done between very close relatives (a father to daughter, or mother to son, etc.). Genetic diversity is severely lacking in a lot of purebred dogs.
Dobermans are not as bad off as some breeds though, and we're lucky to have a lot of truly awesome people working to breed healthier dogs here.
For more info on dog shows and breeding for show dogs, I would definitely go to youtube and watch Pedigree Dogs Exposed
. It's a documentary put out in England about dog shows and breeding practices. Like everything else, go in with an open mind and be sure you read opinions on both sides of the issue because that documentary is produced from just the one point of view. However, that documentary brought up some very good points about the practices of breeding dogs for show. I don't think Dobermans were mentioned, but it's still a good learning point for people.
And also take a look at the LUA Dalmatian outcross
program. There's a case where a deliberate outcross with another breed was done in order to eliminate a serious health problem in Dalmatians. You want a good case study that brought a lot of controversy to a breed, that's surely one of them. But it's a case where they had to ask a question: "Do we want to allow our breed to suffer from a painful health condition that can be fatal in some dogs, or do we want to outcross and then breed back to other Dalmatians in order to eliminate it?" It makes for good reading, if you're interested in how breeds and traits within those breeds are fixed.