I've owned many hound dogs and my hounds, if they pick up a good scent on something interesting, will bolt and they are gone - real gone. Sometimes for days. This is not the characteristic of a good watch dog.
Not to say they can't defend you, they just have to be there first.
When we take our dogs out beyond the fenced area, we have training collars on them. There are many deer in this area and we know that our dogs will chase them if they appear.
When outside, our dogs are either behind a six foot, chain link fence, or on leash. The majority of the time they are in the house, and by our sides. Ridgebacks are extremely loyal and affectionate. They never want to be far from us, but we do recognize that they are prey-driven.