The only time I've seen a dog guarantee die when the master dies, is when playing Search and Rescue, even then it may get Martry Dog first.
For the most part I don't mind them, BUT I think they should make it so you can hear the dog walking around so you have some sort of warning. I know you can hear the dog growl at you, but it doesn't growl when you just killed its owner. So dog footstep sounds would help a lot.
I don't think the dogs are OP, but they are annoying. Sometimes my dog refuses to kill the person who killed me last. If the dogs took one or less mag to kill, then they will be effectiveless.
The dogs are definitely difficult to kill. I usually run with a sniper rifle and it takes 3 rounds to kill the dog and that's on hardcore. Not sure if it takes more rounds on core modes. Can you knife the dog? In close quarters I try but can't seem to get the timing down. However, I'm not a fan of nerfing anything in the game. I think that leads to more problems than it's worth.
learn to stay away from vicious dogs like in real life and shoot from afar...i have been killed by dogs maybe 7 times. Whatever you are doing you are doing it wrong.