Interesting question. Namkar Barzin is part of Dorje Shugden's entourage and the second minister. He is not part of the body mandala of Lama Losang Tubwang Dorje Chang.
Like Thaimonk mentioned, Why have Shakyamuni and then Tsongkhapa...! It is about our affinity. Why have Army, Navy, Air Force, Marine etc? Why have police and FBI? Different roles. Depending on our needs, the medicine is different.
Being an unenlightened protector, he is even closer and "easier" to propitiate. If we can directly connect to the Buddhas, then it is the best but almost all in these degenerate times can't, so protectors are important. In this logic, then unenlightened protectors are closer. But I think we need a guru's guidance and instruction before we can propitiate unenlightened protectors. As NB is part of DS's entourage, I think it is fine as he is very loyal to DS.
