Have to have my two penneth worth on this one, yes there are purpose bred deer dogs and yes in the correct hands they will be brilliant, but so will and Lab, springer or Cocker.
I have 3 Cockers and all work deer, yes they are like a box of frogs on a sugar high, but train them right and they will be dual purpose. Mine have two characters the first is the shoot day pocket rocket and the other is the time to stay to heel and become the calm stalkers friend, they know which job they are on and behave accordingly......its all in the training