Without seeing it directly I have a hard time saying he's bullying or he just never learned to play appropriately.
Dobermans play rough. They mouth around the neck. That IS their play style. What they're doing is natural to them. HOWEVER, it is not always natural to other dogs and there are dogs who certainly don't like that. It sounds to me that he just never learned how to play politely with other dogs.
For me, I watch the other dog's body language to decide whether it's playing or bullying. If the other dog has its hackles up or has its tail between its legs (even while playing) or looks like it's trying to get away, CALL YOUR DOG OFF. If he doesn't respond to you, physically remove him from the game. If he has his mouth around the other dog (like I said, some dogs play by mouthing...Dobes do this), obviously don't pull your dog off, you'll take a chunk of the other dog with you.
For me, light mouthing is ok. Grabbing and holding on is not ok (even though he's probably still just playing). As a puppy we taught our dog that 'easy' means lighten up (with whatever we're doing...walking...taking food...playing). So with her, if she grabs on (she rarely does this anymore as we've worked with her since a puppy), we tell her easy and ideally she'll let go. If she doesn't let go with the 'easy', then we say 'NO' loudly, which she understands as 'stop what you're doing'. If your dog doesn't have commands like this...the first step is more obedience training! Anyhow...a NO is pretty straightforward and even if your dog doesn't understand it, the sharpness of your tone should convey your message. That's when you grab your dog. Like I said, if he's still hanging on, wait until he lets go because his mouthing may not hurt the other dog but you pulling him off while he's still holding on, definitely will.
Also, if your dog gets on top of the other dog, even if they're playing, don't let him stay on top for long. If the other dog doesn't get right up again, CALL YOUR DOG OFF. Or pull him off...in this case it's a lot less likely for there to be mouthing going on so pulling directly off should be ok. Of course, I would always call your dog first and if he doesn't come I would do a sharp 'NO' and then pull your dog off.
If your dog is playing with another dog you should keep a close eye on them at all times. Innocent play can easily turn into a dog-fight if one of the dog does something the other doesn't like or they've just played too long. Like children, sometimes dogs don't understand it's naptime (not literally)! If it looks like one of the dogs is no longer enjoying him/herself, it's time to end the game. Sometimes neither dog knows how to stop, other times one dog is still totally into the game and the other one is tired and ready to quit. That's another time when a game turns into a fight.
Once you've removed your dog from the situation, if you don't have voice-control over your dog, grab onto his leash and put him into a sit or a down (whichever he's more comfortable with). Let him cool down, catch his breath. Sometimes the other dog will run over to investigate. If that happens, get the other owner to call their dog away. You can just explain that your dog is too excited and you want him to calm down a little or whatever you want to say. Dobermans ARE high-energy dogs and strong...they're often not aware of their own strength and some dogs can't match that.
I don't like the idea of doing 'corrections' with other dogs like you mentioned above. My fear with that is that your dog will associate play with other dogs with negative things. That's not something I even want to go near with my dog. I want play to be positive, positive, positive!
Just like being a parent...sometimes you need to teach your kid to share or that it's not OK to push someone. You need to do that with your dog too, teach them how to play properly especially if that learning experience didn't happen as a puppy. If nothing else, the most important thing is to watch for the other dog's body language. Hackles, tail-between-legs, spending too much time on the ground...time to quit.
It's not easy training an adult male doberman how to play so I wish you luck!