Awhile back one of my dogs had that problem too. And, I have to say I did switch food and it went away. Not saying that the same thing is happening to your dog. It was so long ago though and I didn't know about the quality brands of dog food at the time so I'm afraid I can't recommend anything for you. But, I don't think it can hurt if you switch the dog food to a quality brand like Origen, Wellness Core or Innova Evo. That's only three of the quality brands that I like but there are more out there.
There is one thing I forgot to ask.... You said you have a dobie/lab mix. Soooo, my question to you is do you regularly shampoo your dog? If so, that could be an irritant to your dog as well. In the summer, I decided to shampoo my dog and didn't get all the soap off of her in that area and she went crazy w/itching, etc. Her tail is usually up and she left it down for a couple of weeks as she was a little raw.
Did the vet give you some sort of salve to put on it in the meantime for the irritation? It may be harder to determine if the food is helping since Kali may be irritating it more because she is always licking there. Just my thoughts.