I have one acquaintance with a PhD in the dimensions of sheep's femurs and another with a PhD on characteristics of one of the fungi that grow on the decaying foliage taken by leaf-cutter ants into their nests. Often these types of specialist PhDs go on to teach or work in areas other than these specialist areas where they have undoubtedly contributed to the academic knowledge on that subject.
This is were I begin to have a problem with the word "competent". My own research was in a particularly arcane area which really doesn't bear any relation to or help me with the job I do now.
I'm beginning to feel more and more that we have these various "hoops" we are expected to jump through "to reach the required level" that increasingly bear little relationship to what we end up doing. Is it perhaps because people don't have the skills or time to assess knowledge and competence in a more meaningful way?