I'd like to say upfront, I don't know this breeder, and didn't go look at their page<G>
That said. Not everyone involved heavily in Dobermans is a member of the DPCA, and even if they are, they may choose not to pay for a breeder listing, and even then, it's paid ads, do your due diligence, don't accept that ad content in any format or club listing is 'vetted' information. You, the buyer still need to do your homework.
A lot of folks do not show in conformation events. Not to say they aren't working with their dogs, but there is a whole other world out there who focus solely on working ability, and physical and mental soundness for the sport in which they choose to compete. Those breeders and dogs will likely not be listed on a breeder listing with DPCA. Are those breeders focused on health? You betcha, an unhealthy dog is not a good candidate for sport work, or SAR work or or or. The physical and mental demands placed on a working dog are tremendous, and they must be sound enough both in body and mind, to handle the pressures. Are these dogs likely to step foot in an AKC show ring and take it by storm? In most cases, no, they won't. Are they still 'good' Dobermans? Yes they are.
I would say the BEST way to look for a puppy is make a priority list for yourself. Be honest, it's only for your eyes. What are your goals with a puppy? Do you want to get involved in conformation shows? Performance events?(obedience, agility, or other) Sport work? (IPO, French Ring, Mondio) are you looking solely for a laid back companion dog to hang with you? Do you like to camp? Hike? Travel? Attend a lot of social gatherings with your dog? These are all things that will dictate the type of temperament most suitable to your lifestyle. Are dogs bred by breeders who don't compete bad dogs? Nope, not a given at all. A lot of very dedicated breed fanciers are out there, producing the occasional litter of pups out of well health tested parents, with an eye on longevity and mental soundness, and a number of those pups DO go on to compete in various venues with their new owners.
Be very clear in YOUR goals for a dog. Be very clear when sharing those goals with a breeder. Do not go looking for a working line puppy, to hang around and share the couch with you. Will they be happy to do that? Sure, sometimes<G> But they demand a LOT of training and mental stimulation to get to the hang on the couch point. Look for health clearances, cardiac, thyroid, hips, liver, kidney test results. On both parents. I like to have eye clearances as well, some breeders do eyes, some do not. There are reasons for this disparity that I won't go into, but no eye clearance is not always a sign of a 'sketchy' breeder.
Learn to read a pedigree. Learn where the databases are so you can research some things on your own. Dobermans have a ton of databases! A lot of information can be gleaned in this manner, longevity, accomplishments of the parents, pedigree health information, ability to look at the pedigree breadth, as well as depth.Don't be in a hurry to add a pup, they are all adorable, they are all deserving of good homes, but you need to make darn sure you get a pup that fits YOUR life, it's a decade(plus some hopefully!) long commitment, and if you get a nervy, screwy dog, or a dog with a ton of health issues inherent in their makeup, it's a decade long nightmare.