Many people think that a deaf (or blind/deaf) dog needs to have a hearing dog to follow around. This is usually not necessary. Although, if you do have a hearing dog, your deaf dog will watch him closely for cues to things that are important to him – mealtimes, going for a walk, etc. A deaf dog (or even a blind/deaf dog) will notice when the other dogs around him are getting excited, heading towards the door for a walk, or the kitchen for a treat. In fact, sometimes it is even hard to tell which dogs can't hear, as the deaf dog learns to respond just as quickly as the hearing dogs.
A deaf dog will also watch you closely to see what cues you give. Sometimes your deaf dog will notice cues that you aren’t even aware you are giving! They are very good observers! If there are not other dogs in the home for a deaf dog to take its cues from, it will take its cues from you and from other members of the household.
Deaf dogs are individuals, just like people and hearing dogs are. Some enjoy the company of other dogs, while some may not. And some dogs get along with certain dogs and not others. It's not fair to try to push certain dogs to live with other dogs if they aren't comfortable with that. And, just because a dog enjoys playing with other dogs doesn't mean it needs to live with other dogs all the time. It might be just as happy as an only dog that gets to have regular playtime with the dog next door.
There is nothing wrong with having hearing dogs if you adopt a deaf dog. There is nothing wrong with having several deaf dogs together either! Any dogs that live together will develop relationships all their own. Dogs don't really care which dogs can hear and which ones can't.
We as humans love the idea of a dog "knowing" another dog is different and taking on the role as helper. We have a fairy tale image of two dogs developing this type of relationship. And it does sometimes happen and is a magical thing to watch. But don't pair up two dogs with the expectation that one will take on the role of helper to another.
In reality, this very rarely happens. The dogs will develop a relationship, but normally it is not the hearing dog helping the deaf dog at all. Normally it is the deaf dog learning to read the hearing dog's behaviors and what they mean.
I have also lived with deaf and blind/deaf dogs long enough that I have seen them step into a helper role with my other hearing dogs on occasion. Their ability to see and hear (or not) in no way hindered them from helping another dog in a useful manner.
Please don't rely on myths when choosing dogs to live together. Instead, take into account each dog as an individual. Make choices based on each one's personality and what personality of dog would be a good match for the household and for the other dogs. If you choose to live with a single dog, please don't ever feel guilty or sad about that, as your dog will be thrilled to have all your time and attention, and will learn to watch you just as closely for information as it might have learned to watch the other dogs.